on-line vs online

on-line and online both are adjectives.

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

As adjectives, on-line and online are synonyms defined as:

on-line and online: connected to a computer network or accessible by computer

As adjectives, on-line and online are synonyms defined as:

on-line and online: on a regular route of a railroad or bus or airline system

As adjectives, on-line and online are synonyms defined as:

on-line (adjective)	online (adjective)
connected to a computer network or accessible by computer	connected to a computer network or accessible by computer
on a regular route of a railroad or bus or airline system	on a regular route of a railroad or bus or airline system
being in progress now	being in progress now