later vs later on

later is an adjective but later on is not an adjective.

Word	Noun	Adjective	Verb	Adverb
later	No	Yes	No	Yes
later on	No	No	No	Yes

As adverbs, later and later on are synonyms defined as:

Other synonyms of later include after, afterward, afterwards, subsequently.

later (adjective)	later on (adjective)
at or toward an end or late period or stage of development
coming at a subsequent time or stage

later (adverb)	later on (adverb)
happening at a time subsequent to a reference time	happening at a time subsequent to a reference time
at some eventual time in the future
comparative of the adverb `late'