younger vs jr.

younger and jr. both are adjectives.

Word	Noun	Adjective	Verb	Adverb
younger	No	Yes	No	No
jr.	No	Yes	No	No

As adjectives, younger and jr. are synonyms defined as:

younger and jr.: used of the younger of two persons of the same name especially used to distinguish a son from his father

Other synonyms of younger include Junior.

younger (adjective)	jr. (adjective)
used of the younger of two persons of the same name especially used to distinguish a son from his father	used of the younger of two persons of the same name especially used to distinguish a son from his father