gnat vs mosquito

gnat and mosquito both are nouns.

Word	Noun	Adjective	Verb	Adverb
gnat	Yes	No	No	No
mosquito	Yes	No	No	No

As nouns, mosquito is a hypernym of gnat; that is, mosquito is a word with a broader meaning than gnat:

gnat: (British usage) mosquito
mosquito: two-winged insect whose female has a long proboscis to pierce the skin and suck the blood of humans and animals

gnat (noun)	mosquito (noun)
any of various small biting flies: midges; biting midges; black flies; sand flies	two-winged insect whose female has a long proboscis to pierce the skin and suck the blood of humans and animals
(British usage) mosquito