timing vs simultaneity

timing and simultaneity both are nouns.

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

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

timing (noun)	simultaneity (noun)
the regulation of occurrence, pace, or coordination to achieve a desired effect (as in music, theater, athletics, mechanics)	happening or existing or done at the same time
the time when something happens