collection vs compendium

collection and compendium both are nouns.

Word	Noun	Adjective	Verb	Adverb
collection	Yes	No	No	No
compendium	Yes	No	No	No

As nouns, collection and compendium are synonyms defined as:

collection (noun)	compendium (noun)
the act of gathering something together	a concise but comprehensive summary of a larger work
a publication containing a variety of works	a publication containing a variety of works
request for a sum of money
several things grouped together or considered as a whole