starting time vs birth

starting time and birth both are nouns.

Word	Noun	Adjective	Verb	Adverb
starting time	Yes	No	No	No
birth	Yes	No	Yes	No

As nouns, birth is a hyponym of starting time; that is, birth is a word with a more specific, narrower meaning than starting time:

Other hyponyms of starting time include incipience, incipiency, starting point, terminus a quo, threshold.

starting time (noun)	birth (noun)
the time at which something is supposed to begin	the event of being born
	a baby born; an offspring
	the process of giving birth
	the kinship relation of an offspring to the parents
	the time when something begins (especially life)

starting time (verb)	birth (verb)
	cause to be born