constabulary vs police force

constabulary and police force both are nouns.

Word	Noun	Adjective	Verb	Adverb
constabulary	Yes	No	No	No
police force	Yes	No	No	No

As nouns, constabulary and police force are synonyms defined as:

Other synonyms of constabulary include law, police.

constabulary (noun)	police force (noun)
the force of policemen and officers	the force of policemen and officers