An infant (from the Latin word infans, meaning “unable to speak” or “speechless”) is the more formal or specialised synonym for “baby”, the very young offspring of a human. The term 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, newborn or neonate (from Latin, neonatus, newborn) refers to an infant in the first 28 days after birth; the term applies to premature, full term, and postmature infants; before birth, the term “fetus” is used. The term “infant” is typically applied to young children between one month and one year of age; however, definitions may vary and may include children up to two years of age. When a human child learns to walk, the term “toddler” may be used instead.
In British English, an infant school is for children aged between four and seven. As a legal term, “infancy” continues from birth until age 18.
A newborn’s shoulders and hips are wide, the abdomen protrudes slightly, and the arms and legs are relatively long with respect to the rest of their body. In first world nations, the average total body length of newborns are 35.6–50.8 cm (14.0–20.0 in), although premature newborns may be much smaller. The Apgar score is a measure of a newborn’s transition from the uterus during the first minutes after birth.