by-line vs sideline

by-line and sideline both are nouns.

Word	Noun	Adjective	Verb	Adverb
by-line	Yes	No	No	No
sideline	Yes	No	Yes	No

As nouns, by-line and sideline are synonyms defined as:

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

by-line (noun)	sideline (noun)
an auxiliary activity	an auxiliary activity
a line giving the name of the writer of a story or article	an auxiliary line of merchandise
	a line that marks the side boundary of a playing field

by-line (verb)	sideline (verb)
	remove from the center of activity or attention; place into an inferior position