The Math Forum

Ask Dr. Math - Questions and Answers from our Archives
Associated Topics || Dr. Math Home || Search Dr. Math

Use of Plural with Decimal Numbers

Date: 02/27/2002 at 09:37:12
From: Eric Derobert
Subject: Use of plural with decimal numbers

Hello !

For natural numbers, the use of plural is of course easy :

0 point, 1 point, 2 points, 3 points...

But what happens when using decimal numbers between 1 and 2 ?
What are the rules for 1.0001, 1.1, 1.5 or 1.999 ?

Should we write 
1.0001, 1.1, 1.5, 1.999 point
1.0001, 1.1, 1.5, 1.999 points ?

Thank you !

Date: 02/27/2002 at 12:32:59
From: Doctor Peterson
Subject: Re: Use of plural with decimal numbers

Hi, Eric.

I believe you are asking whether, in English, we treat various numbers 
as singular or plural. My understanding is that we consider ONLY the 
number 1 as singular; in particular, zero is a plural: we say "0 
degrees" or "0 (no) apples," not "0 degree" or "0 apple." We do not 
use fractions as adjectives at all, but say "half (of) an apple" or 
"two thirds of a degree" with the fraction standing alone as a noun 
phrase, so it would not be quite accurate to say that a proper 
fraction is singular. With a mixed number, we tend to use a plural: 
"one and a half apples."

Applying these ideas to decimals, I would say

    0.5 apple (half an apple, five tenths of an apple)
    0.9 apple
    1.1 apples
    1.5 apples

In other words, anything greater than one can be taken as plural, as 
well as zero and possibly negative numbers. But in many cases the 
plural might be used with decimals smaller than 1; I have no strong 
objection to "0.5 meters".

I have not found a reference to support any of my advice, which is 
based mostly on what feels right to me.

- Doctor Peterson, The Math Forum   

Date: 02/27/2002 at 13:09:41
From: Eric Derobert
Subject: Use of plural with decimal numbers

Dear Dr Peterson,

In fact, I did some research from my 1st asking, and the rule appears 
to be different in English and in French (I am from France).

In French the rule is to use plural for a noun when the number before 
is greater or equal to 2 (see this official reference from Quebec-
Canada :   ).

From the

   Guide to Grammar and Writing    

I found a different rule : when the absolute value of a fractional or 
decimal expression is 1 or less, the word it modifies should be 
singular (that's exactly what you apply in your 4 apples examples).

   "When fractional or decimal expression are 1 or less, the word
    they modify should be singular: 0.7 meter, 0.22 cubic foot,
    0.78 kilometer. Precede decimal fractions with a value less than
    one with a leading zero before the decimal point."

But also, when you say that singular applies only to 1, the examples 
you propose seem very familiar : I've heard "0 degrees", and I've read 
"0.5 meters"...

Apparently, the rules then depend on languages and uses... But 
perhaps, some official rule exists for English as a whole ?

How interesting !

Kind regards.

Date: 02/27/2002 at 14:31:13
From: Doctor Peterson
Subject: Re: Use of plural with decimal numbers

Hi, Eric.

English (and especially American English) has no "official" rules for 
anything, though there are many "experts" who claim to give such 
rules. But with or without regulation, this is definitely a linguistic 
issue rather than one of mathematics or logic. Each language has a 
different set of rules for number as well as other aspects of grammar 
- for example, some languages have not only a singular and a plural, 
but a "dual" for exactly two, which would raise additional questions 
when applied to, say, 2.001. Different rules may be equally logical, 
and different languages may have different needs.

Here is another reference I found (from Germany, but referring to 

Vocabulary Box: SI Units of Measure(ment)   

    With a few exceptions, plurals of spelled-out units are formed
    conventionally. Use the singular form with numbers less than or
    equal to 1, and use the plural form with numbers greater than 1.
    (In spoken English, however, decimal numbers take the plural
    form even if they are less than 1, e.g. "a quarter second" but
    "zero point two five seconds.")

This shows that both of the rules I gave have their place.

- Doctor Peterson, The Math Forum   

Date: 02/27/2002 at 16:57:13
From: Doctor Peterson
Subject: Re: Use of plural with decimal numbers

Hello, Eric!

I looked again and found that although your Quebec URL referred only 
to the main page (because the source uses a frame), another link takes 
me to a FAQ with the answer you described:   

Here is a translation:

    Agreement of the noun after a fractional number less than two 

    The noun that follows a fractional number less than two, such as 
    one and a half, does not take the plural. Contrary to the English 
    use, the name million, when one writes 1,5 million, remains in the
    singular. Moreover, the oral pronunciation shows that it is about 
    a unit: one million five hundred thousand. 

    The rule of agreement is the following: a name preceded by a
    number takes the plural only when this number is equal to or
    greater than two. 

    Here are some examples: 

    1,3 billion people (it is necessary to say: a billion three
    hundred million people); 

    1,47 meter (it is necessary to say: one meter 47); 

    An average of 1,25 child by household (it is necessary to say:
    a child and a quarter). 

Note that "the English use" for "million" differs from the American 
usage; the English say "1.5 millions," but we Americans use the 
singular no matter how many million it is.

I suspect that the reason for the French rule lies in the way you say 
the number. You say the whole part, then the unit (million, meter, 
child), then the fractional part (three hundred million, 47, quarter). 
So if the whole part is one, you use the singular, and if it is two or 
more you use the plural. We think of the entire number as more than 
one and therefore plural; you use only the whole part as a direct 
modifier, which is NOT more than one in these cases, though a fraction 
is then added to it. The difference is entirely in the grammar, which 
determines the choice of words.

Another page gives some related ideas on fractions:

    La foire aux questions linguistiques   

In English we tend always to think of the fraction as a number in 
itself, rather than as a phrase, and to emphasize agreement in meaning 
rather than form; we would never say "2/3 of the road are open," even 
though grammatically the subject of the verb is the plural "thirds."  
But we would say "2/3 of the students are present," because there must 
be more than one student. On the other hand, the British would say 
"2/3 of the class are present," while an American might prefer 
"2/3 of the class is present," because we tend to treat collective 
nouns as singular. Language has its reasons, but they are not always 
in agreement.

Of course, this is entirely a grammatical matter in French, and mostly 
a logical issue in English (that is, we aren't thinking of grammar, 
but only of whether more than one is under consideration). So in 
French this usage with fractions disagrees with the "two or more are 
plural" rule, because the grammar differs in the two cases, whereas in 
English we more consistently focus on the meaning.

I've enjoyed looking into this issue, even though it is really a 
question for Dr. Linguistics.

- Doctor Peterson, The Math Forum   

Date: 02/28/2002 at 05:23:05
From: Eric Derobert
Subject: Use of plural with decimal numbers

Dear Dr Peterson,

Thank you for spending such an amount of time to answer this 
paramathematical topic ! This is very complete.

I think you are right when emphasizing the role of the way of saying 
numbers : "1.50 meters" in English and "1 metre 50" in French, which 
is written "1,50 metre" for consistency.

Kind regards, and thank you again !

Associated Topics:
Elementary Number Sense/About Numbers
Middle School Number Sense/About Numbers

Search the Dr. Math Library:

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.