A newspaper ran this headline recently:
(1) Police crack down on IAC protesters. [emph added]
Why did it not read:
(2) ? Police cracks down on IAC protesters.
I have found instances of
police cracks in newspapers: "Police cracks whip" and "Chesterfield police cracks down on drunk drivers". However, google's ngram viewer suggests that
police cracks is significantly less frequent:
I think that the difference between
Police _crack_ down and
Police _cracks_ down is influenced by subject-verb agreement and that the difference in this example reflects the grammatical number of the verb's subject. Here,
cracks is inflected for singular number, which implies that its subject is singular, and
crack is inflected for plural number, which implies that its subject is plural. E.g.:
The army cracks down on IAC protesters. [singular]
The armies crack down on IAC protesters. [plural]
The confusing thing about (1) and (2) is that the subject,
police, looks like it is singular; the plural form would be
polices, but I have never heard this form (for the noun).
It sounds like
police fits the definition of a collective noun, which Wikipedia says is "the name of a number (or collection) of people or things taken together and spoken of as one whole. For example, in the phrase 'a pride of lions', pride is a collective noun."
Police fits this because it refers to (i) some relevant police force or (ii) some relevant group of police officers, which are both collections of people taken as wholes. It does not refer to a single police officer.
So one might conjecture that verbs whose subjects are collective nouns are inflected for plural number. However, it sounds like
group also fits the definition of a collective noun because it refers to a collection of individuals taken as a whole. And I think that both of the following sound acceptable.
(3) The group crack down on IAC protesters.
(4) The group cracks down on IAC protesters.
The above conjecture also doesn't explain why it is sometimes okay to use
My preliminary questions: Do (1), (2), (3) and (4) all sound acceptable to everyone else? Are
group both collective nouns?
My main questions: If (3) and (4) are both acceptable and
group are both collective nouns, then why does (1) but not (2) sound acceptable, or at least why is
police crack better than
police cracks? How do you determine the correct conjugation for a verb whose subject is a collective noun? Is there a general rule, or does it vary from case to case?
My secondary questions: Does the behavior of (1) and (2) have to do with synesis? Is using
police to refer to the police force more like a synecdoche or other kind of rhetorical trope? Does it matter if you add
(5) The police crack down on IAC protesters.
(6) ? The police cracks down on IAC protesters.
I ask these secondary questions because I find it interesting that
police is, to me, a near synonym of
police force, but
police force (ngram verb comparison) behaves oppositely to
police (ngram verb comparison) when it comes to subject-verb agreement:
(7) ? The police force crack down on IAC protesters.
(8) The police force cracks down on IAC protesters.
[Note: the question mark at the beginning of an example indicates questionable grammaticality.]