respiratory rate vs vital sign

respiratory rate and vital sign both are nouns.

Word	Noun	Adjective	Verb	Adverb
respiratory rate	Yes	No	No	No
vital sign	Yes	No	No	No

As nouns, vital sign is a hypernym of respiratory rate; that is, vital sign is a word with a broader meaning than respiratory rate:

respiratory rate: the rate at which a person inhales and exhales; usually measured to obtain a quick evaluation of a person's health
vital sign: sign of life; usually an indicator of a person's general physical condition

Other hypernyms of respiratory rate include rate.

respiratory rate (noun)	vital sign (noun)
the rate at which a person inhales and exhales; usually measured to obtain a quick evaluation of a person's health	sign of life; usually an indicator of a person's general physical condition