forthcoming vs approaching

forthcoming is not a noun while approaching is a noun.

Word	Noun	Adjective	Verb	Adverb
forthcoming	No	Yes	No	No
approaching	Yes	Yes	No	No

As adjectives, forthcoming and approaching are synonyms defined as:

Other synonyms of forthcoming include coming, upcoming.

forthcoming (noun)	approaching (noun)
	the act of drawing spatially closer to something
	the temporal property of becoming nearer in time
	the event of one object coming closer to another

forthcoming (adjective)	approaching (adjective)
available when required or as promised	of the relatively near future
of the relatively near future
at ease in talking to others