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My 5-year-old asked this morning if you would say a road was "thin" or "narrow". We had no difficulty telling her she should use "narrow" in that case, but couldn't explain why.

We found it impossible to come up with a definitive rule-of-thumb or set of rules-of-thumb that didn't have too many obvious exceptions. And yet it does seem like there is a reasonable general agreement on which adjectives are appropriate/best in which circumstances. Are people just learning every individual instance, or are there actual sensible correlations?

There are some interesting theories in this discussion but nothing citing any references, and no real conclusion was drawn.

So why might a thin person have a narrow waist? (ngram) *

Or why can pipes be either thin or narrow, but straws in general not? (ngram)


* I also wonder what happened circa 1980 that accounts for the huge increase in "narrow waist"!

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why can pipes be either thin or narrow, but straws in general not? I'd use both for straws, but I wouldn't say a pipe was thin. –  starsplusplus Jul 20 at 14:45
@starsplusplus interesting. There's definitely an element of personal preference, which doesn't help with getting a definitive answer. Did you check out the ngram though? Here's one just for "straw" goo.gl/GHYflL –  CupawnTae Jul 20 at 16:08
Interesting. Narrow straw does seem less common, in written English at least. –  starsplusplus Jul 20 at 16:12
Its not a hard and fast rule, but narrow usually connotes an interior perspective, while thin is usually used for external perspectives. A straw is "narrow" because something has to go through it, whereas a rod is "thin" because it may need to be held or fitted into something. –  RBarryYoung Jul 20 at 19:40
+1 for the question! –  Drew Jul 20 at 20:45

4 Answers 4

Having mulled this over in my head for a bit, I finally came—through the help of @starplusplus’ comment—to a distinction which I think holds up quite nicely in the vast majority of cases. There will always be odd ones out that are just completely idiomatic and do not hold up to logical scrutiny (many, in fact—this is language we’re dealing with), but the following tallies with both my instinctive, hard-to-verbalise gut feeling and also nearly all the examples I can come up with.


Narrow and broad (or wide) emphasise one dimension, while thin and thick emphasise (or can emphasise, depending on the notional shape of the object described) two dimensions.

All of these words are used (non-figuratively) of three-dimensional objects, and they both tell us something about two of these dimensions: they tell us nothing of length, but they do say something about width and depth.

Objects that do not have a particular, notional ‘surface’

When you use thin/thick, you are giving no particular importance to width and depth in relation to each other—their values are implied to be equally distributed, or any difference in their values is considered unimportant. (Though see below)

When you use narrow/broad, on the other hand, you are ascribing particular importance to one dimension (width) over the other (depth); or, in some cases, you are describing that one dimension (width) in particular has a higher or lower value that normally seen. Depth is either not considered relevant, or is considered relevant only as the value against which the narrow/broad thing is compared.

Thus for example, neither narrow ribbon nor thin ribbon tells us anything at all about the length of the ribbon in question. But where thin ribbon tells us only that the width and depth dimensions have small values—leaving aside as unimportant whether they are in fact identical values or not—narrow ribbon tells us nothing much about the depth dimension of the ribbon, but only the width dimension, which is said to have a smaller value than normally seen (in the archetypal, prototypical ribbon that of course looks different in everyone’s mind).

Objects that have a particular, notional ‘surface’

If something is of such a shape that we consider one of its surface areas to be the surface (such as tables, mattresses, or perhaps even ribbons), thin/thick is often used almost contrastively to narrow/broad in that it then emphasises the depth dimension in the same way that narrow/broad emphasises the width dimension. I would say that this is a narrowing (!) down of the two-dimensional meaning to one dimension, for the simple reason that we just do not talk about the dimensions of objects that we consider to have a single ‘important’ surface with indiscriminate regard to the relationship between the dimensions.

Consider a mattress as an example. It has a surface, which is always the side that faces up on our beds. We may wish to describe the length, width, or depth of the mattress individually, but there is no practical need to ever describe collectively the width and depth of it with no real distinction between the two.

Consider then instead a wooden beam. We don’t generally consider beams to have just one surface—all four sides (excluding the ends) are equally important, because no one of them has a particular, inherent usage. We may still wish to address all three dimensions individually, in which case we still use narrow/broad to refer to the width dimension, and thin/thick to refer to the depth dimension; but if there is no implied or explicit comparison with the width dimension, then thin/thick can still quite easily be used in its more generic, two-dimensional sense, to indicate that both the width and depth dimensions of the beam have relatively high values, regardless of what the exact relationship between these values are.


(Incidentally, in this view, I don’t consider narrow waist to be so irrational after all: you are simply commenting specifically on the width dimension, which is of course the diameter from the left side of the body to the right; i.e., someone with a narrow waist looks narrow from the front, but not necessarily from the side. Thin waist would instead refer to someone who looks thin from all sides.)

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I’m glad you don’t consider narrow waist “irrational”: it’s the top-ranked collocation for ADJ waist in COCA. Here are the top twenty, with their citation counts: narrow:68, tiny:51, small:50, slender:32, slim:26, elastic:22, trim:22, thick:18, thin:18, nipped-in:11, cinched:10, drawstring:9, wide:8, lean:7, tapered:6, adjustable:6, thickening:5, ample:5, defined:5, smaller:5. –  tchrist Jul 20 at 15:54
+1 A piece of paper can be both narrow and thin. Its narrowness is a function of the relationship between length and width. Its thickness is unidimensional and really is a comparison to other papers of this sort. –  bib Jul 20 at 16:34
@bib that's apples and oranges though. A better comparison would be thickness vs breadth, and then that difference disappears. A piece of paper's thinness is not the same thing as its thickness - a very large (areawise) piece of paper will seem thinner than a smaller piece of the same thickness. Conversely, a 100x10 piece of paper would probably be deemed narrower than a 150x11 piece. My point is that both thinness and narrowness are subjective terms that will at times be affected by other dimensions, and other times apparently not. –  CupawnTae Jul 20 at 19:13
Perfect definition, makes total sense! –  Vixen Jul 21 at 8:33

The words are similar, but usually not inter-changeable.

Thin is an adjective that describes an object's characteristic width or depth:

"This pencil is thin; that pencil is not."

"This type of pasta is thin; the other is not."

"The mattress is thin and lumpy."

"We use thin-film technology in the production of solar cells."

Narrow is an adjective that describes an object's characteristic channel size:

"The hallway is narrow, but the foyer is wide."

"The river is quite narrow near the falls."

There are colloquial exceptions, as you pointed out such as narrow-wasted. Some objects can be both thin or narrow, such as the stripes on my tie.

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Except that "thin" often refers to depth: thin layer, thin surface, etc. And in those cases, you might use "narrow" to refer to the width. E.g. a thin mattress or tabletop might be wide or narrow. So sometimes it seems like maybe it's just because "thin" was already used in another sense/for another dimension. –  CupawnTae Jul 20 at 13:31
@Cupawn I'm not really sure those are exceptions or differ that much, really. A mattress or table top also has a kind of ‘channel size’. Narrow (and wide) have more to do with the amount of space available on the surface (or other relevant part) of the object for the use or position of something relative to it. Thin and thick have more to do with circumference seen as a whole (or any single dimension of a circumference), but from a purely measuring point of view, rather than from the point of view of using the space the circumference allots for something physical. –  Janus Bahs Jacquet Jul 20 at 13:40
Narrow waist is really the only truly bizarre exception I can think of that isn't figurative (such as narrow escape, which still gives an idea of a surface-like concept that has an inadequate area—here the space between being caught and escaping). Narrow really makes no logical sense to me with waist; it is simply idiom. –  Janus Bahs Jacquet Jul 20 at 13:45
@JanusBahsJacquet ok, to use one of the examples from the answer, look at the ngram for "thin pencil" vs "narrow pencil" goo.gl/0m7G4x - not that clear-cut at all, and in fact "narrow pencil" was considerably more common for much of the 20th century. Maybe the confusion is that there is an area of overlap, with "narrow" never concerning depth, and "thin" never concerning capacity, but many cases where either works, then just dictated by fashion... –  CupawnTae Jul 20 at 14:09
I'd say that's quite accurate: there is quite a bit of overlap where fashion gets to have the last say. Narrow pencil sounds almost bizarre to my ear, but apparently not to many others’. Conversely, I am quite happy to think of both wide oak trees and thick oak trees, even though I'm describing the circumference of their trunks. Wide just sounds more poetic and Tolkienesque here. –  Janus Bahs Jacquet Jul 20 at 14:13

To address part of your question/s, thin refers to depth and narrow to width. As an example of the rule, a ribbon would always be considered to be thin (not thick), but could be narrow or wide as to its width. A road could be thin or thick with regard to its paving--but I doubt that is the dimension your daughter is trying to identify. When describing the relative width of the road, narrow or wide would be appropriate. However, as pointed out by other commenters and posters, thin is commonly used to describe objects that have a round cross section-- thin spaghetti, thin strands of hair, etc. With a round cross section, the distinction between depth and width is lost.

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It's definitely not that simple. Interestingly, @GarysStudent's answer says the opposite about "thin" and gives examples. Other examples: thin line, thin fingers, thin thread, thin stem... –  CupawnTae Jul 20 at 13:23

To add to the fray -

  • Narrow can be used to contrast with wide; thin cannot. At least two dimensions are involved.

  • Thin can be used to contrast with thick; narrow cannot. One dimension is stressed, even though it is the other dimension(s) that are qualified by the adjective.

A line or a string can be more or less thin/thick. We think of a line as essentially linear, ideally one-dimensional. IOW, we deemphasize its thickness or width, even though that is what we are talking about.

A band of cloth or a street can be more or less narrow/wide. We recognize both dimensions (length and breadth) as important.

(And yes, I realize that this is, or at least appears to be, the opposite of what @JanusBahsJacquet said here:

Narrow and broad (or wide) emphasise one dimension, while thin and thick emphasise (or can emphasise, depending on the notional shape of the object described) two dimensions.

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