apparel vs article of clothing

apparel and article of clothing both are nouns.

Word	Noun	Adjective	Verb	Adverb
apparel	Yes	No	Yes	No
article of clothing	Yes	No	No	No

As nouns, article of clothing is a hypernym of apparel; that is, article of clothing is a word with a broader meaning than apparel:

Other hypernyms of apparel include clothing, habiliment, vesture, wear, wearable.

apparel (noun)	article of clothing (noun)
clothing in general	a covering designed to be worn on a person's body

apparel (verb)	article of clothing (verb)
provide with clothes or put clothes on