premie vs preterm baby

premie and preterm baby both are nouns.

Word	Noun	Adjective	Verb	Adverb
premie	Yes	No	No	No
preterm baby	Yes	No	No	No

As nouns, premie and preterm baby are synonyms defined as:

premie and preterm baby: an infant that is born prior to 37 weeks of gestation

Other synonyms of premie include preemie, premature baby, premature infant, preterm infant.

premie (noun)	preterm baby (noun)
an infant that is born prior to 37 weeks of gestation	an infant that is born prior to 37 weeks of gestation