Languages having only a singular and plural form may still differ in their treatment of zero. For example, in English, German, Dutch, Italian, Spanish and Portuguese, the plural form is used for zero or more than one, and the singular for one thing only. By contrast, in French, the singular form is used for zero.
https://en.wikipedia.org/wiki/Plural
There is some logic to suggest that in English "zero" is neither singular nor plural - here is an example:
If the number one is used, whether it is +/-1, the following noun will be singular. So it would be -1 apple. We’re talking grammar, not logic; and yes we say zero apples, probably because zero is thought of as a number that is not one, even though zero is neither singular nor plural logically.
Unfortunately mathematical theory may have little correlation with grammar or usage. The concept of grammatical number is not a mathematical concept strictly, so the word one is always singular, whatever mathematical theory may hold.
English probably treats zero as a plural because the grammar gives only two choices, and the word zero is not the word one: we also say, incidentally, there are no apples on the table (countable) but we say there is no rice on the table (uncountable).
http://neilwhitfield.wordpress.com/2007/10/31/good-question-are-fractions-and-decimals-singular-or-plural/
