premature infant vs preterm infant

premature infant and preterm infant both are nouns.

Word	Noun	Adjective	Verb	Adverb
premature infant	Yes	No	No	No
preterm infant	Yes	No	No	No

As nouns, premature infant and preterm infant are synonyms defined as:

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

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

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