Question

If I have zero complaints, why is the subject plural? If I have one complaint, it is singular. How can zero be plural?

Answer 1

Think of zero as "no". Let us substitute zero with no.
1 apple, no apples.
1 person, no people.
You can't say no apple or no person. So it is the same thing with zero. You can't zero apple or zero person. We usually say there is not a single person here but we don't say there is zero person here.
One apple means one apple but zero apples could mean zero out of many that were there before. In other words, we had four apples in the bowl but now they are all gone. So we have zero apples left. If there was one left, we would say, we have one apple left.

Answer 2

Nah, I still don't get it. How can something that is not plural still only have agreement with a plural noun. Maybe it is a Math question, rather than an English question.

Answer 3

Maybe. I suppose numerical values have nothing to do with grammar rules. It's the same in Spanish.

Answer 4

In the sentence, 'zero' is an adjective. Adjectives are words that describe how many, the characteristics, or other aspects of an object/subject.

I have zero complaints.
subject verb adjective object

Therefore, the subject ("I") is always plural...the object changes from singular to plural based on the number.

Answer 5

*is always singular