tit vs tomtit

tit and tomtit both are nouns.

Word	Noun	Adjective	Verb	Adverb
tit	Yes	No	No	No
tomtit	Yes	No	No	No

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

tit: small insectivorous birds
tomtit: widely distributed European titmouse with bright cobalt blue wings and tail and crown of the head

tit (noun)	tomtit (noun)
small insectivorous birds	widely distributed European titmouse with bright cobalt blue wings and tail and crown of the head
either of two soft fleshy milk-secreting glandular organs on the chest of a woman
the small projection of a mammary gland