on-line vs current

on-line is not a noun while current is a noun.

Word	Noun	Adjective	Verb	Adverb
on-line	No	Yes	No	No
current	Yes	Yes	No	No

on-line (noun)	current (noun)
	a steady flow of a fluid (usually from natural causes)
	dominant course (suggestive of running water) of successive events or ideas
	a flow of electricity through a conductor

on-line (adjective)	current (adjective)
connected to a computer network or accessible by computer	occurring in or belonging to the present time
on a regular route of a railroad or bus or airline system
being in progress now