MAOI vs antidepressant drug

MAOI and antidepressant drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
MAOI	Yes	No	No	No
antidepressant drug	Yes	No	No	No

As nouns, antidepressant drug is a hypernym of MAOI; that is, antidepressant drug is a word with a broader 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
antidepressant drug: any of a class of drugs used to treat depression; often have undesirable side effects

Other hypernyms of MAOI include antidepressant.

MAOI (noun)	antidepressant drug (noun)
any of a group of antidepressant drugs that inhibit the action of monoamine oxidase in the brain and so allow monoamines to accumulate	any of a class of drugs used to treat depression; often have undesirable side effects