premenstrual syndrome vs PMS

premenstrual syndrome and PMS both are nouns.

Word	Noun	Adjective	Verb	Adverb
premenstrual syndrome	Yes	No	No	No
PMS	Yes	No	No	No

As nouns, premenstrual syndrome and PMS are synonyms defined as:

premenstrual syndrome and PMS: a syndrome that occurs in many women from 2 to 14 days before the onset of menstruation

premenstrual syndrome (noun)	PMS (noun)
a syndrome that occurs in many women from 2 to 14 days before the onset of menstruation	a syndrome that occurs in many women from 2 to 14 days before the onset of menstruation