An infant or baby is the very young offspring of human beings. Infant is a formal or specialised synonym for the common term baby. The terms may also be used to refer to juveniles of other organisms. A newborn is, in colloquial use, an infant who is only hours, days, or up to one month old. In medical contexts, a newborn or neonate is an infant in the first 28 days after birth; the term applies to premature, full term, and postmature infants.

नुकत्याच जन्मलेल्या बाळाला नवजात अर्भक (Infant) म्हणतात, व त्याच्या आईला बाळंतीण. त्याचे वय २८ दिवसांचे होईपर्यंत नवजात म्हणतात. २८ दिवसांपासून ते ३ वर्षांपर्यंत बाल्यावस्था व ३ ते १६ वर्षांपर्यंत किशोरावस्था म्हणतात.