birth vs vaginal birth

birth and vaginal birth both are nouns.

Word	Noun	Adjective	Verb	Adverb
birth	Yes	No	Yes	No
vaginal birth	Yes	No	No	No

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

birth: the process of giving birth
vaginal birth: the parturition process in human beings; having a baby; the process of giving birth to a child

birth (noun)	vaginal birth (noun)
the event of being born	the parturition process in human beings; having a baby; the process of giving birth to a child
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)

birth (verb)	vaginal birth (verb)
cause to be born