preemie vs preterm baby

preemie and preterm baby both are nouns.

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

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

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

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

preemie (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