Why don't we pluralize "foot" in measurements?

For example, to answer the question, "How tall are you?" valid answers include:

• Five feet.
• Five foot three.
• Five feet, three inches.

Why the discrepancy between feet and foot, seemingly only in the second case.

This question is inspired by this question: "Forty foot" or "forty feet"?

edit: I do not believe the answer to this is related to the other question. The explanation for the other question is because of how adjective modifiers work. My question is a very different case, unrelated to adjectives. My observation is that I am asking about a particular exception case which applies only when "foot" is followed by a number which is assumed to be inches. That's extremely specific, and I doubt that the etymology has any relation to why we leave adjective modifiers singular.

• It's not a duplicate. The answer on compound adjectives doesn't apply here. It's not exactly inspiring though. Commented Jun 3, 2011 at 23:19
• I'm intrigued you think the choice of foot or feet is affected by whether or not there are any odd inches following. I've never come across that distinction before, and in fact I'd be quite happy to answer "Six foot - well, six foot two, to be precise". Commented Jun 4, 2011 at 1:40
• Maybe I'm wrong. Am I? I also have the impression that it's only for feet -- no other unit of measurement. "One meter seventy-five" doesn't sound right to me. Commented Jun 4, 2011 at 1:57
• My father's a builder, and I've worked with him on lots of 'diy' jobs where we've had to call measurements out. I'm sure he'd always say "One meter seventy-five", as would I. Or more likely just "One seven-fifty" to avoid confusion about whether the 'minor' component was centimeters or milimeters. We're UK; maybe US usage differs. Commented Jun 4, 2011 at 2:08

I think it's "idiomatic by association".

The above NGram should be enough to at least prove a trend - but this one for five feet / foot six is even more clear-cut.

There's long-standing 'idiomatic' use of the singular noun-form in 'adjectival' compounds such as toothbrush, ten-foot bargepole, four-wheel drive, etc. The answer to "how tall are you?" isn't really a noun, and it isn't a verb. It's closest 'basic' linguistic element is in fact an adjective (describing your height). People sense this, so over the decades they've simply shown an increasing tendency to apply the same 'singularisation' rule they've always been used to in related contexts.

OP correctly identifies a tendency to use the older pluralised form with more 'precise' measurements. One reason may be that people speak more carefully knowing they've got the longer utterance to come. Without conciously thinking, they just override the 'idiomatic' tendency in favour of the 'older, but perhaps more accurate' plural. The ones who do that are decreasing all the time, but obviously most of us would avoid pluralising the explicitly-named inches if we hadn't already pluralised feet.

It's the same with UK x pounds y pence (and US X dollars y cents, maybe?), where you often hear the first unit singularised and the second omitted. I suspect there's an increasing tendency to omit both units just to avoid the awkwardness of possible mixed plurality.

• Adjectival modifiers are irrelevant to this question. Commented Jun 4, 2011 at 1:04
• So I think to summarize this, my observations are flawed and basically we do this because we consider it an adjectival function. I wonder then if we should hyphenate "five-foot-four" then? Commented Jun 4, 2011 at 9:01
• @tenfour: Not I don't think your observations are flawed. I'm sorry I was so ungracious last night, but on calmer reflection the usage you've pointed out does occur, and I believe is explicable. So far as I'm aware now, the only point we might disagree on is that I think most standard responses to "How tall are you?" are 'adjective-like' in most speakers minds. But you may be prepared to agree with that now. Commented Jun 4, 2011 at 13:50
• Wow...so many downvotes for something not obviously bad. Commented Dec 10, 2016 at 18:48
• @Mitch: You might find the edit history interesting! I assume that initially some people didn't like my dismissive original text Yawn - of course it's idiomatic, but I suspect at least some of the subsequent downvotes (including some today) are from people who just don't like me! As for the NGram text, it's just that if I'd included two inches the "trend" I'm trying to highlight wouldn't be so marked. Nevertheless, there definitely is a trend, and I'm perfectly happy to defend this answer against all comers (unless and until some genuine objection is raised! :) Commented Dec 10, 2016 at 19:03

There are many such cases of using singular forms for plural meaning, not only in English, but also in German, and possibly other Germanic languages, or even non-Germanic languages. For example, you order "drei Bier" instead of "drei Biere", and in a football match, there are "elf Mann" on the pitch, rather than "elf Männer". (The plural forms are not strictly incorrect, just less common.)

In general, the "why" question doesn't have a satisfactory answer for this kind of linguistic fact; don't search for logic and reason where there's only history and convention.

Ah, and of course you also say "drei Fuß" in German (on the rare occasion you'd be referring to pre-metric measures), not "drei Füße", which, in this case, would have to be qualified as wrong, just as in English, I guess.

• I'm not terribly keen on all German examples to answer a question about English. Commented Jun 3, 2011 at 23:14
• I'm not terribly keen on the fact that the only non-Germanic part of this answer freely admits the "why" question doesn't have a satisfactory answer. But I get three downvotes for saying the same thing without the pointless window-dressing. Commented Jun 3, 2011 at 23:41
• @z7sg - I hope there are other things you're terribly keen on! :-) Did you know English is a Germanic language? Still shows, after all these years ... :-) So, the brother of "keen" in German is "kühn", which means audacious - isn't that fascinating?
– Lumi
Commented Jun 3, 2011 at 23:47
• @FumbleFingers I think it's an honest effort by a new user, although ultimately not a suitable answer so I didn't downvote. Your answer otoh is just a snarky comment. Commented Jun 3, 2011 at 23:51
• The question was "why". I don't know the answer, but the answer could easily be along the lines of "because English is a Germanic language, and features X and Y entered both English and German from their common ancestor". So demonstrating similar behaviour in German is a perfectly valid thing to be doing, as part of the answer to a "why" question about English.
– user16269
Commented Jan 19, 2012 at 11:04

While, to my ear, the distinction you mention sounds right, it is not quite supported by what we see in published literature.

For example, both of the following are attested as replies to How tall are you?, and I'm not sure one is significantly more frequent than the other:

[1] a. I'm about five f̲o̲o̲t̲ ten. (sources)
b. I'm just five f̲e̲e̲t̲ two. (sources)

Similarly, both of the following are attested as well:

[2] a. I am five f̲o̲o̲t̲ two inches tall. (sources)
b. I am five f̲e̲e̲t̲ three inches tall. (sources)

In CGEL, for example, we find both of the following:

[3] a. Our room is twenty f̲e̲e̲t̲ by thirty f̲e̲e̲t̲ (p. 655)
b. My other table is six f̲o̲o̲t̲ by four. (p. 693)

Just in case one is tempted to think it significant that in [3a] the unit appears twice while in [3b] the second appearance it is ellipted, note that e.g. the following are attested:

[4] a. Heizer's Double Negative is a 50 f̲o̲o̲t̲ by 30 f̲o̲o̲t̲ by 1,500 f̲o̲o̲t̲ double cut in Virgin River                  Mesa, Nevada. (sources)
b. Here is likewise a court-yard 40 f̲e̲e̲t̲ by 37. (sources)

I conclude that the distinction under discussion is regional or idiolectical---that it doesn't really exist in Standard English. It seems that in Standard English, both foot and feet are acceptable in the present context, though in other contexts it may not be so (e.g. it is definitely a ten-f̲o̲o̲t̲ pole, not a *a ten-f̲e̲e̲t̲ pole; see here).

• @Elliot Despite the fact that the sample sentences come from published literature, and that, if you click on the links for sources, you can see the results of searches on Google books? If you'd said it wasn't exactly scientific because it is not based on a scientifically established corpus, I'd agree. But the only opinion involved, I would say, is the belief that the selection of texts on google books is reasonably representative of what educated native speakers would write. Commented Sep 20, 2020 at 22:34

I'm not sure the addition of inches matters much, as I've heard it both ways for straight foot/feet measurements as well. My best guess is that it has to do with an implied adjective vs. noun. For example:

When a person says "I'm 6 foot" my mind hears it like an adjective, similar to "I am a 6-foot man" where the person has colloquially dropped the "a" and the hyphen and the noun is implied by whoever is doing the speaking.

When a person says "I'm 6 feet" my mind hears it like a noun, similar to "I measure 6 feet" where the dimension of measurement is implied.

In writing, it helps to use hyphens and commas as necessary to clear up the meaning (e.g. "6-foot, 2-inches" adjective vs. "6 feet and 2 inches" noun, but in speech they can sound almost identical other than the singular/plural usage.

The ability to choose between the singular and plural form of foot/feet is common to several other measurement words, and may be a quality of some non-metric measurement words.

First, this usage seems superficially similar to the compound usage of other measurements, where they appear to be in a singular form because they describe how long / big / heavy something is. Compare:

In all of these uses, the measurement and number are an attribute of the noun. So it's possible that this attributive usage has been generalized to frequently-used forms of measurement like "five foot three" when nouns are absent. As a result, in these idiomatic circumstances, adjusting the count of the measurement word is optional.

I can think of a few other examples of count-ambivalence among non-metric units of measure. These examples show this kind of usage is hundreds of years old, whatever its origin may be:

Stone - occurs in both singular and plural historically:

Pound - specific to money, and an example of idiomatic usage with currency:

• Singular: "the Sum of Ten Pound, over and above the said Four Shillings" (Source from 1801)
• Plural: "For the best four year old steer, fifteen pounds, Mr. J. A. Drought" (Source from 1808)

Mile - same pattern

Foot, too, follows a similar pattern. After running a search for "six foot three," I found the following examples:

• Singular: "The portrait had some points of resemblance, and six foot three was just his height" (Source from 1851)
• Plural: "Then the average would be Six Feet Three, but not Thirteen Feet" (Source from 1800)

In other words, English has had this idiomatic usage for a while. Why is something idiomatic? Usage over time is enough to answer that for foot.

feet is the unit of measurement. feet, pounds, miles
not
foot, pound, mile
*She is five feet 3. This does not work because feet is not a unit of measure yet it becomes okay to use if you specify a unit of measurement such as inches after 3.

If there are no nouns following the unit, then it is:

Six feet

but if there are any noun following:

six foot four inches

or

A six-foot hole/A six-foot drop,

but

but, : six feet tall.

The reason the last example is "feet" is because although it is followed by another word, that word is an "adjective".

A six-foot man/ a man who is six feet tall.

We can also see this in other measurements:

Six-inch ruler/six inches long.

25-mile journey/ 25 miles long.

• Typesetting note: hyphens make the distinction clearer. Six-inch is adjectival, six inches is nominal. Commented Jun 4, 2011 at 7:42
• I think people don't like the 'mixed plurality' of six foot four inches. I agree with @Jon Purdy on the adjectival/nominal distinction, where nominals invariably use singular units. But the answer to "How tall are you?" isn't really a 'nominal' in that sense, which is why it gets speakers a bit confused sometimes. Commented Jun 4, 2011 at 14:17
• @FumbleFingers: In speaking, I would consider the use of the singular "foot" with number greater than one, in contexts where the phrase is used as a noun, to be an indication that it will be followed by a number of inches, with the number of inches implied. Thus "Bob stood five feet eleven inches tall" or "Joe stood six feet tall", but "Larry stood six-foot three". I would consider both "five foot eleven inches" and "six feet three" to be awkward. For measurements below two feet I would either use inches or, if reasonable in context, fractional feet (e.g. "a foot and a half" or "1.5 feet"). Commented Jan 19, 2015 at 19:39