GABA vs neurotransmitter

GABA and neurotransmitter both are nouns.

Word	Noun	Adjective	Verb	Adverb
GABA	Yes	No	No	No
neurotransmitter	Yes	No	No	No

As nouns, neurotransmitter is a hypernym of GABA; that is, neurotransmitter is a word with a broader meaning than GABA:

GABA: an amino acid that is found in the central nervous system; acts as an inhibitory neurotransmitter
neurotransmitter: a neurochemical that transmits nerve impulses across a synapse

Other hypernyms of GABA include amino acid, aminoalkanoic acid.

GABA (noun)	neurotransmitter (noun)
an amino acid that is found in the central nervous system; acts as an inhibitory neurotransmitter	a neurochemical that transmits nerve impulses across a synapse