timing vs approaching

timing and approaching both are nouns.

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

As nouns, approaching is a hyponym of timing; that is, approaching is a word with a more specific, narrower meaning than timing:

timing (noun)	approaching (noun)
the regulation of occurrence, pace, or coordination to achieve a desired effect (as in music, theater, athletics, mechanics)	the act of drawing spatially closer to something
the time when something happens	the temporal property of becoming nearer in time
	the event of one object coming closer to another

timing (adjective)	approaching (adjective)
	of the relatively near future