MAOI vs phenelzine

MAOI and phenelzine both are nouns.

Word	Noun	Adjective	Verb	Adverb
MAOI	Yes	No	No	No
phenelzine	Yes	No	No	No

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

MAOI: any of a group of antidepressant drugs that inhibit the action of monoamine oxidase in the brain and so allow monoamines to accumulate
phenelzine: monoamine oxidase inhibitor (trade name Nardil) used to treat clinical depression

Other hyponyms of MAOI include iproclozide, isocarboxazid, Marplan, Nardil, tranylcypromine.

MAOI (noun)	phenelzine (noun)
any of a group of antidepressant drugs that inhibit the action of monoamine oxidase in the brain and so allow monoamines to accumulate	monoamine oxidase inhibitor (trade name Nardil) used to treat clinical depression