custom vs usage

custom and usage both are nouns.

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

As nouns, custom and usage are synonyms defined as:

Other synonyms of custom include usance.

custom (noun)	usage (noun)
accepted or habitual practice	the act of using
habitual patronage	accepted or habitual practice
a specific practice of long standing	the customary manner in which a language (or a form of a language) is spoken or written
money collected under a tariff

custom (adjective)	usage (adjective)
made according to the specifications of an individual