usage vs employment

usage and employment both are nouns.

Word	Noun	Adjective	Verb	Adverb
usage	Yes	No	No	No
employment	Yes	No	No	No

As nouns, usage and employment are synonyms defined as:

Other synonyms of usage include exercise, use, utilisation, utilization.

usage (noun)	employment (noun)
the act of using	the occupation for which you are paid
accepted or habitual practice	the act of using
the customary manner in which a language (or a form of a language) is spoken or written	the act of giving someone a job
	the state of being employed or having a job