Jakob Nielsen is the usability guru who hardly needs an introduction. But for the sake of completeness we’ll mention he’s the co-founder of the California-based consultancy, Nielsen Norman Group, and has been crusading against bad web design for years through his biweekly column, The Alertbox, and his numerous books. He’s brought usability to the attention of the general public, but within the user experience community he’s been criticized by those who say he emphasizes a puritanical view of utilitarianism that excludes other dimensions of user experience. Oh, and did we mention he’s the man who launched a thousand parody sites?
So is Nielsen the defender of ease-of-use or the enemy of creativity? We talked to the controversial Dane, and you might be surprised…
B&A: What are some of the toughest design challenges on the web today?
Nielsen: I think to get a really big jump in usability, because I think we can make a website that can show a few things quite well, if you have a few products. We can also do a huge database and you can search it, and it works reasonably well.
But I don’t think we really have a handle on getting the average person through the vast number of things that a website can offer. If you narrow it down and show a few things, yes, if you assume that they are capable doing a lot of data manipulation. But I think there’s a large number of cases that do not fall into one of those two categories. You can go to CNN and see the five big headlines of the day, and that works fairly well. You can go to Amazon and you can buy my book, for example, if you know the name of the book. But in the intermediate case of having a website with 10,000 articles and finding the one that’s right for you, which is quite often the case on a tech support website … basically doesn’t work at all.
B&A: What types of research interest you the most?
Nielsen: How to get usability out to the masses. When I say masses, I mean web designers, not users. Right now we have about 30 million websites, and we will have up to 100 million in three to five years. That’s a large number of design projects. How many usability people are there in the world who are in any way qualified? At the most, maybe 10,000 or so.
Therefore, we know that we’re not going to have this number of web projects done according to the recommended old methodology. So, even what I’ve been pushing in the past—more efficient, quick usability methodologies—is not good enough when you have that number of design projects. We need to have several orders of magnitude improvement in the efficiency of usability to really impact that number of design projects. Can we do things like encapsulate usability knowledge in guidelines such that an average designer can actually apply them?
B&A: What do you feel is the relationship between a usability professional and a designer?
Nielsen: I think they could play two different roles: either that of an editor and a writer, or a professor and a student.
In the more integrated projects, which is the preferred way to do it, I think it’s more like the editor and the writer, where the designer will come up with things just as the writer would write the article, and the editor will make it better, will know what the readers need and how to present it in a good way and help the writer improve their article. I have never met a professional writer who didn’t like to have a good editor. There often seems to be a conflict between designers and usability people, but I think that once you conceptualize it as the usability person helping to improve the design, then I think it goes away.
But you’re going to have a lot of designers who don’t have a usability professional in their team. So the vast majority of them just have to learn what the principles are that work well with users from usability professionals, and then it becomes more of an educational mission. So the relationship is more like that of the professor and the student. The student is the one who has to go do it at the end of the day, but the professor is the one who has the knowledge, having had done all the research in the past and can tell the student what works well.
B&A: How do you react to designers who have strong feelings about usability in one way or another?
Nielsen: I think that designers that don’t want usability are misguided because it’s really just a way of helping them achieve a better design. Some of them just reject the goal of having a design that’s easy to use. If you have the goal of a design as actually trying to accomplish something, then you’re more in the art world, and if the project doesn’t have a goal, then maybe it’s appropriate—design for design’s sake. But if you do design to actually accomplish something, then I’d argue that it has to be easy to use, so I don’t think that it’s appropriate to reject the goal of usability if your project has to accomplish something. Design is creating something that has a purpose in life; art is creating for the sake of creating — that’s my distinction between those two terms.
Whether they want to get usability from someone who knows about it, or whether they want to find it out themselves … can be debatable. How did any of us become usability specialists in the first place? Only by doing a lot of the research and studies. Any designer could do that as well if they bothered. They don’t have to get it from us, but then I would argue that they would need to do it themselves.
B&A: Is there a particular reason you advocate for using guidelines? I’ve heard people say that it comes off as overly dogmatic to simply have a huge list of guidelines.
Nielsen: Experience says that usually these work — usually, but not always. Usability guidelines always need to be applied with a certain amount of understanding as to when they apply and when they don’t apply. If a set of guidelines is written well, then usually they will apply, and it will be the exception when they don’t apply. You have to acknowledge that on one hand it may be that only 90 percent of the guidelines apply … so you can’t violate all guidelines, you can only violate some if you have a good reason to do so.
Some people may not understand the difference between a guideline and a standard. A standard is something that is 100 percent firm, and a guideline is something that is usually right — that’s why it’s called a guideline.
B&A: What’s the difference between a standard, a guideline, and a heuristic?
Nielsen: You get even more vague when you get into the area of heuristics. Heuristics are things that are rules of thumb, so they are very vague and very broad. At the same time, they are very powerful, because they can explain a lot of different phenomena, but that explanation has to be done with a lot of insight, and that is what’s more difficult. One of the lessons from a lot of my research is that heuristic evaluations indicate how to adjust an interface relative to these general principles of good usability. It’s fairly difficult to do well. Anybody could do it to some extent, but they couldn’t necessarily do it very well, and you have to have a large amount of experience to do it well.
On the average design project today, they don’t have that amount of usability expertise on their team, and therefore we’ve got to give them something more complete that it’s easier for them to deal with. It’s a matter of the usability of the usability principles, really. If we make them more specific, they become more concrete, they’re easier to interpret, and … easier for the designers to judge when they do not apply.
B&A: What’s the difference between someone doing a heuristic evaluation solo versus doing it in a team?
Nielsen: The way I developed heuristic evaluations back in the 1980s was meant to be an interaction between solo and the team, because you first do it individually, and then you combine a few people who have done the heuristic evaluation. That’s done very rarely, because it’s rare that a project team will have that many people on board who really know about usability.
“(I)t’s not a matter of intuition. It’s a matter of being very good at pattern matching, being able to spot small things, and hold together the big picture of what that really means.”
A common mistake about heuristics is thinking that it’s just a list of complaints. It’s not a list of complaints, it’s a list of issues relating back to the underlying fundamental principles. When you say that this button is wrong or this flows wrong, you say it’s wrong because it violates this well-known usability principle. And then, of course, people can argue. They can say, “no, it does not violate this principle,” and then you would have a discussion about that, which is a great method of illuminating and getting insight into the design.
B&A: What are the most important skills for a usability specialist to have?
Nielsen: I would say experience. It’s an unfortunate thing to say, because you can’t acquire experience other than by doing it. This is a discipline where you will always start off being bad and you end up being good. You only get to be good by slogging through several initial projects where you didn’t do that well, and then you get better and better. I think that being a truly great usability specialist comes from having 10 years of experience and having seen a very large number of different designs, different technologies, different types of users — a very broad variety of experience.
The benefit of usability, though, is that it is such a powerful method, and the return on investment is so huge that even if you don’t do that great a job at it —maybe you don’t get a return of 100-to-1 and you only get a return of 20-to-1 — that’s still a huge return investment. Even the very first usability project someone does, and they mess up everything, it’s still going to be positive, and it’s going to be a great learning experience for them personally, and their team is going to get value out of the investment as well. Just keep doing it and doing it and doing it.
It’s very much of an analytical and interpretive discipline as well. Intuition is completely the wrong word to use — it’s not a matter of intuition. It’s a matter of being very good at pattern matching, being able to spot small things, and hold together the big picture of what that really means. That’s where experience helps you — it helps you to do pattern matching and match patterns you’ve seen before, and the more things you’ve seen before, the better you can do that.
There’s definitely a big evangelizing and propaganda component as well, so having good communication skills is very important too.
B&A: Are there any usability specialists you particularly admire or whom you took guidance from?
Nielsen: I did actually. I’ll say that two of them are actually colleagues at my company, Don Norman and Bruce Tognazzini. They are two incredibly great people. Another one I’d like to mention who’s now retired is John Gould. He worked at IBM in the 1980s. He developed a lot of the early approaches and for any question you could come up with he’d say, “OK, you can do a study of that.” He was just such an empirical guy that it was incredible.
Another person is Tom Landauer, who worked at Bell for many, many years. I was privileged to work with him for four years when I worked there as well. He was very much on the measurement side: “We can quantify this. We can estimate these things.”
I’d like to mention one more person … I never worked with, Ted Nelson, who was the guy who kind of invented hypertext. He got me into this feeling that we shouldn’t accept computers being difficult, that computers can be a personal empowerment tool. I read a lot of his writings when I was in grad school. His writing is really what got me going in this area in the first place back in the 1970s.
B&A: How many users do you yourself observe in the average month?
Nielsen: I probably sit with too few users, actually. Probably less than 10. It ought to be many more. In my own defense, I’ll say that I’ve done it for many years, and the learning is cumulative. I run a lot of projects where someone else will sit with the user, but I’ll still monitor very closely what goes on. I would still say that it’s very important to sit with the user as well. People should continue to do that forever — you never get enough of that. In particular, for someone who’s starting out in usability, I would say 20 or 30 a month would be a good goal to have, so that you can try to run a study every week.
B&A: Will there be new methodologies for user research in the future, or will we keep refining the ones we have right now?
Nielsen: I think mainly we will keep refining the ones we have. Of course, you never know if some completely new thing will come up, but I think it’s not likely. The classic methodology was developed in the 1970s and early 1980s. John Gould was one of the big people doing that and I learned a lot from him. That was pretty much established by then: how to do measurement studies and all that.
“Usability has very much seemed like a black art … Many things are testable, but at the same time we have to broaden the scope to make it even cheaper, even more accessible, get even more people doing it.”
Then, in the late 1980s, I reacted a bit against my own mentors and said, “These are all great methods, but they take too long, and a lot of projects won’t do them if they’re not at a big, rich company like IBM.” So, we developed discount usability methodologies, which was a faster way of doing these things.
Since 1990 there hasn’t been that much change. I think it’s pretty slow-moving because it doesn’t relate to technology, which changes all the time. It relates to humans and the process of accommodating human needs, which doesn’t change very much.
B&A: Do you ever feel like discount usability methods can be misused?
Nielsen: I think there could be cases where someone does a heuristic without truly understanding the principles. Or you might have someone who tests one user and says, “Let’s go with that.” But in general I think that the methods are so powerful that they actually hold up pretty well even if they’re abused.
I read recently somebody who had criticized the idea of doing studies with a small number of users with the argument that you cannot judge the severity of the usability problems because you don’t have enough instances of observation to know the frequency with which it occurs. This is a circular argument, a self-fulfilling prophecy because you are accepting in their argument that the only way you can judge the severity of a problem is by having a statistically accurate assessment of it’s frequency. I’m arguing that after having had observed it a few times, you can, with the insight that comes from experience, estimate the severity pretty well — good enough anyway. The real issue in severity ratings is that you’ve got to do a cost-benefit analysis.
B&A: What’s your take on information architecture?
Nielsen: The first question I have is what it really even is. I tend to operate under the definition that it’s the structuring of an information space. I view that as being different from information design, which has to deal with how you present the information once you’ve found it, or interaction design, which is a matter of flow through a transaction or task. I know that some people like to use the words information architecture to apply to everything, which is what I would tend to call user experience. That’s purely a matter of what terminology you feel like using. I tend to think that user experience is built of these components: how are things structured, how it is presented, how do you flow through it, and other things like how is it advertised.
B&A: What’s next for you and the Nielsen Norman Group?
Nielsen: Trying to drive usability more broadly toward that larger set of design firms, really trying to encapsulate it to make it more portable. Usability has very much seemed like a black art. I myself have often said, “Well, you can just test that.” Well, that is true. Many things are testable, but at the same time we have to broaden the scope to make it even cheaper, even more accessible, get even more people doing it.
There’s another trend as well which is tackling deeper issues that have been neglected in the past that need to be more in the forefront. Things like users with disabilities, international users, much more focus on task analysis and field studies — those are some of the other things we’re pushing now.
Recently I’ve been pushing the notion of doing discount field studies. Field studies don’t need to consist of five anthropologists taking a year to do a project. We’ve had a seminar at our conference on simplified field studies, which I personally think is a good seminar. But, empirical data shows that people don’t want to do this. You can go to the conference and see people crammed into sessions on everything else, but then you go into the field studies seminar and there’s only 30 people or so. We are pushing it, but we’re not getting enough acceptance of this idea of the simplified field study.
B&A: Who do you think does a good job dealing with content online?
Nielsen: Very few actually. I can’t come up with any great examples — it’s still so print-oriented. My own articles aren’t that great either, actually. I’m very verbose in my writing style. It needs to be very punchy and very short, and it’s very hard to write that way.
There’s more linking happening today with all of the weblogs, which is kind of nice, but I think the commentary is often not that great. The reason is that I think weblogs tend to emphasize this stream of consciousness posting style, which I don’t think is good—that’s not respectful of the readers’ time. What’s good about weblogs is that they’ve broadened the number of authors, but at the same time they’ve removed that feeling that the writing is really being edited.
B&A: If you weren’t doing usability, what do you think you’d be doing?
Nielsen: I would probably be a university professor of something or other. When I think back to when I was a kid, I had a lot of different interests and things I was good at, which I think was one of the reasons I ended up in usability. You have be good at communicating, you have to know about technology, you have to understand interaction and human behavior. There’s all these different angles that pull together very nicely in usability. It’s good for a person who’s broad in the types of things they’re good at.
I might have ended up as a historian, I might have been a mathematician, I don’t know. I think that being a professor is the most likely. The reason I got into usability is that it’s a discipline that gets interesting when you go into the actual practice of it. There’s actually not that much theory, and it’s not that exciting actually.
I was at the same time interested and disappointed by Jakob’s response to the question of “who do you think does a good job…”
Although I interpreted the question as referring to “good design” it seems that perhaps Jakob was thinking about “good writing”? In any case I was pleased to hear that he doesn’t think that is own work is all “that great either, actually.”
However it raises the concern that if no one is going a good job at something, then perhaps the way of measuring that something is faulty? I know that I’m not pleased with much of my own work (my personal site especially), however I am able to point to others that I feel are going a good job.
Does anyone else feel that there should be examples of “good jobs” in this online world or ours?
“Content” in web development typically refers to the text content of a web page, which is how Mr. Nielsen responded. The visual design/presentation of that content is a separate thing.
I think it’s entirely possible that no one is doing a good job of content creation or visual design, but I do not agree it is that way now. I believe this was very true about 5-7 years ago before there was an Internet boom; back when web pages were typically developed as a side task by DBA’s, MIS people and software engineers.
Now that teams of writers, editors and designers (the appropriate people IMHO!) are being brought into web development, I think that both content creation and visual design/presentation have improved a great deal.
“Good design” is directly related to the creator’s intent. You have to be able to measure the creator’s intent in order to measure if the design is “good”. And yes, I believe there can be examples of good jobs in this online world, provided the result is properly compared to the intent in order to adequately illustrate what makes it good.
Jakob said: “…if the project doesn’t have a goal, then maybe it’s appropriate—design for design’s sake. But if you do design to actually accomplish something, then I’d argue that it has to be easy to use, so I don’t think that it’s appropriate to reject the goal of usability if your project has to accomplish something.”
But what Mr. Nielsen fails to acknowledge is that designs (whether on Web or somewhere else) *all* have goals–and often, that “art for art’s sake” *can* be the goal!
It is a gross assumption that a generic, task-oriented, “ease-of-use” is always the end goal! Things like branding, marketing, building consumer awareness, emotional identification with a product/service, creating or sustaining an emotional response–those are ALL goals of design! They are in the realm of design!
And unfortunately, Nielsen’s usability principles don’t even *touch* these areas. He explains in his book that he isn’t an expert in these disciplines, but I believe a wiser approach would be *acknowledging* those weaknesses, and pointing to experts who *do* draw on the vast knowledge that print design and advertising have created.
Sure, the Web is *not* print, but we still have much to learn from our dead tree predecessors.
And those things *do* fall under the category of usability and design–designers are *paid* to create emotional interaction, brand recognition, awareness–and few of these are easily quantifiable! These esoteric things are critical, but not as easy to measure with stats and bulleted top-10 lists, which is why I believe they don’t show up on useit.com.
These are areas of usability and e-commerce design that *cannot* be ignored. And unfortunately for many companies and others who take Jakob’s advice as gospel, it *will* come back to haunt them.
I have yet to see JN comment on Patterns : a way of writing guidelines that express the circumstances of use, recognises the forces involved, and describes the resulting context.
While he does say “Experience says that usually [guidelines] work — usually, but not always. Usability guidelines always need to be applied with a certain amount of understanding as to when they apply and when they don’t apply”, he doesn’t seem to be advocating documenting when to break the rules. He simply refers to experience and reason.
Has he discussed Patterns somewhere? What’s his take on the patterns movement?
Crusader against bad web design?
Just wondering:
Did anyone actually visit his site useit.com before deciding to interview him?
Those who can, do.
Those who can’t, teach.
Those who can’t teach, teach gym
(or something like that, according to Woody Allen.)
If Woody had said that recently, he might have referred to web design instead of phys-ed. And Jakob Nielsen just might be the gym teacher of web design.
A visit to Jakob’s Site is like a study in art theory run amuck. How many 7-year-olds did it take to put that one together?
“Hey Bobby, let’s do the top in bright-lemon-yellow, the kind that makes you squint like when you stare at the sun!” says Suzy.
“Yeah,” says Bobby, “and let’s do half the page in funny blue-green, the kind that makes you want to throw up, and the other half in some ugly light-tanish color!”
If you wonder why he chose those colors and annoying layout, just send Jakob an email and ask him.
All you have to do is:
– scroll to the bottom of his page,
– highlight his email address “nielsen@nngroup.com”,
– right click,
– click on “copy”,
– open your email program,
– paste his address into your email message,
– and fire away!
A usability expert that doesn’t even bother to make his email address a link? (No, it’s not because of email harvesters, they’ll find it anyway even without the link.)
I’m sure Jakob’s a bright guy, and he definitely has some valid points.
But an expert on usability and web design?
I don’t think so.
He may have fooled some corporate big-wigs with deep pockets, but he doesn’t fool me.
Oddly, I had to search to find it, then guess at the url to get the actual page because the search engine didn’t return the page url, just a recap of the page. Anyway, http://www.useit.com/about/whynomailto.html there is the answer — it’s his way of filtering spam. Apparently he needs some help integrating his search engine, too.
I don’t care if JN can design or not, some of the things that he brings up are valuable if for no other reason than they provoke discussion and make people think about the purpose of their sites and focusing their efforts.
I couldn’t find his email address either – and his search engine sucks big time. But as for saying he doesn’t know what he’s talking about…
If anyone out there creates websites and hasn’t done user testing, then your site doesn’t work properly.
Trust me on this, you will not believe some of the things I have seen people do. Example – 1 in 10 users WILL NOT click on an arrow shaped button, or on a > sign – they’ll click to the side where it points. Or about 1 in 20 increases the font size straight away – unless you’ve stopped them…
Every time I have done any kind of testing, something shows up – usually something you wouldn’t expect…
I agree that he goes a bit too far in many cases – but the only way to find out is to test with the right people, getting them to do real things they would really do – thats what he’s getting at, the guidelines etc are just the results of all his testing, for those who can’t be bothered (or can’t convince the client to pay)!
Nielsen, for those of you who don’t know, has never professed to being a Web designer. There is an entire article on the UseIt site that speaks to why the site looks the way it does.
And if you read his work regularly, you know that he does not believe ease-of-use is the only goal of any Web site. He is an extremely practical man in his approach to the role of usability in the overall process of Web design.
He is, however, a usability engineer. That is what he brings to the table to share with the rest of us who may not have that training and experience in our backgrounds. I have always admired his willingness to bend the twig and make provocative statements that get the rest of us engaged in discussion.
Rather than expect one man to have all of the answers or exemplify perfection, we practitioners need to figure out what is known about usability and how we apply it to design.
Can we use UI patterns or Web patterns in the same way developers use patterns for database design or functional design? How would we define those patterns? How would we educate people about them and distribute them?
Yeah, JN has earlier fooled a lot of academic usability practitioners to think that heuristic evaluation can be used to evaluate interfaces. Unfortunately the heuristics have very little use in the real world (they have never been connected to the definition of usability) and they predict about 10-30 precent of real user problems – they are just shots in the dark by the evaluator using himself (herself usually as the usability seems to be a very soft and feminine subject) as a usability test guinea pig. The evaluator never goes beyond his/her own knowledge by the help of the heuristics into the finer workings of the interface.
I think his web guidelines stem from the same family of usability babble (not my term but a web developer’s).
usability guru wrote:
> Yeah, JN has earlier fooled a lot of academic
> usability practitioners to think that heuristic
> evaluation can be used to evaluate interfaces.
I really don’t think this is an accurate or fair assesment of Nielsen’s involvement with heuristic evaluation. I don’t believe that he has ever argued that it should or could replace usability testing.
But usability heuristics are a great starting point, both for evaluation and design. Do you really want to run expensive usability tests to identify obvious problems? I find the 10-30% number perfectly plausible, but assuming it is accurate I think it would be well worth applying a heuristic evaluation to remove the problems it identifies–particularly since it seems quite likely that these will be amongst the most serious problems, the sort that make it difficulty to garner any data from your test other than to identify those problems.
Furthermore, if these heuristics are used by the designers, then you will end up with a better starting point from which to conduct usability tests.
Beyond that, surely an iterative process of running usability tests and then refining the heuristic guidelines (taking into account the various variables) will ultimately lead to better heuristic guidlines that can identify more problems. Surely it is better to prevent problems from occuring than to find and fix them after the fact!
Also, at this point most web sites (although probably not most web pages) are privately maintained by individuals who are most unlikely to run usability tests. Surely these people can benefit from usability heuristics . . .
I agree about some of the points, but along the few random valid results we are getting from heuristic evaluation we are getting a mass of completely wrong judgements which will very severely compromise our professionality as usability evaluators if we present them to the developers. Even the wording of the heuristics encourage very naive remarks about the subject under assessment which totally ignore user’s problem solving ability and willingness to learn.
I appreciate very much Jakob Nielsen’s work as a pioneer (there is a few honest remarks about HE in his articles to be found and also many of his articles meander around the important topics in HCI and usability engineering/evaluation), but I also conflictingly object to perpetuating the usability evaluation’s greatest lie – which is heuristic evaluation.
I may not fully agree with heuristic evaluation, but I like the sentiment behind it – i.e. we desparately need to find ‘discount’ methods of usability that can be done quickly and give useful results within an industrial setting. This is one area of research that I wish was being pursued – discovering quick usability tools, that have an acceptable degree of validity and provide results that businesses find useful.
Until interaction design gets more widely accepted, and built into the whole project life cycle, we need these ‘halfway house’ measures.
I have the same problem in the field I work in: e-learning. There are all sorts of good practices that don’t actually get practiced because they are seen to take too long and not provide enough business value. The practices are actually very similar to usability practices: observation of users in work context, continual dialogue and feedback from learners during development, contextual analysis, observation, etc.
Pragmatic tools and techniques that are quick, cheap and show value never take long to be endorsed by industry.
Sherlock
Usability is great in its place. The thing to remeber the internet is entertainment, hobbies, buisiness…
That means the term usbility needs to have a broad definition in respect to the internet designs. I own a small company http://web-design-companies.com a TradUR.com site and my goal is to make the customer happy. Sometimes it means I have to bite my tongue to give the customer what they want. I can offer subtle suggestions but “The Customer is Always Right.”
Usability is great in its place. The thing to remember, the internet is entertainment, hobbies, buisiness…
That means the term usbility needs to have a broad definition in respect to the internet designs. I own a small company http://web-design-companies.com a TradUR.com site and my goal is to make the customer happy. Sometimes it means I have to bite my tongue to give the customer what they want. I can offer subtle suggestions but “The Customer is Always Right.”
“B&A: Who do you think does a good job dealing with content online?
Nielsen: Very few actually. I can’t come up with any great examples — it’s still so print-oriented. My own articles aren’t that great either, actually. I’m very verbose in my writing style. It needs to be very punchy and very short, and it’s very hard to write that way”
Agreed.
I think content often falls in love with it’s own sense of importance, whereas the reader has no sense of that – at least not initially. They scan before they establish importance – like they do a newspaper.
In short, get straight to the point 🙂
I want to start writing for other sites, does anyone have any suggestions?
Jakob Nielsen’s heuristic evaluation is a mythical reminder that we’re all human.
This was an interesting read, for sure. I’m always pleasantly surprised to see IA and usability discussed in the same space.
Although Nielsen’s writing is (self-admittedly) verbose, he did drive some interesting points home. Nielsen’s response to Chad’s question on his “take on IA” offered a good clarification on the terms information architecture, information design, and interaction design. And it makes complete sense: first, define an information space; define how information will fit within the space; define the the flow through the information within the space.
There is so much bickering that goes on in the field about which title means what, which is more accurate, descriptive, professional, etc etc. Viewing the design process from a linear (chronological) perspective, as Nielsen does in this example, serves to differentiate and clarify these oft-confusing terms.