spare-time activity vs by-line

spare-time activity and by-line both are nouns.

Word	Noun	Adjective	Verb	Adverb
spare-time activity	Yes	No	No	No
by-line	Yes	No	No	No

As nouns, spare-time activity and by-line are synonyms defined as:

Other synonyms of spare-time activity include avocation, hobby, pursuit, sideline.

spare-time activity (noun)	by-line (noun)
an auxiliary activity	an auxiliary activity
	a line giving the name of the writer of a story or article