by-line vs spare-time activity

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

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

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

Other synonyms of by-line include avocation, hobby, pursuit, sideline.

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