That's what I mean about grammatical number and grammatical number agreement.
这就是我所说的语法数字和语法数字一致性。
英语百科
Grammatical number
In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions (such as "one", "two", or "three or more"). In many languages, including English, the number categories are singular and plural. Some languages also have a dual number or other arrangements.