This is your guide to all-round Infant Health, Infant sleep habits, Infant care & feeding, Infant health, development & safety. The word infant comes from Latin word infans, and this means "speechless", the term is typically applied to young children between the ages of 1 month and 12 months. When the baby learns to walk the term toddler is used instead of infant. In medical terms a newborn or neonate refers to an infant in the first 28 days after birth. The term neonate is from Latin and means newborn.