Infant

Part of a series on
Human growth and development
Stages
Gamete Zygote Embryo Fetus Infant Toddler Child Preadolescent Adolescent Emerging and early adulthood Young adult Middle adult Old adult Dying
Biological milestones
Fertilization Pregnancy Childbirth Walking Language acquisition Puberty Menopause Ageing Death
Development and psychology
Pre- and perinatal Infant and child Nature versus nurture Adolescent Youth Young adult Adult Maturity
Developmental stage theories
Attachment Ecological Psychosocial Psychosexual development Moral Cognitive Cultural-historical Evolutionary
Psychology portal
v t e

In common terminology, a baby is the very young offspring of human beings; while infant (from the Latin word infans, meaning 'baby' or 'child'^[1]) is a formal or specialised synonym. The terms may also be used to refer to juveniles of other organisms. A newborn is, in colloquial use, a baby who is only hours, days, or weeks old; while in medical contexts, a newborn or neonate (from Latin, neonatus, newborn) is an infant in the first 28 days after birth^[2] (the term applies to premature, full term, and postmature infants).

Infants born prior to 37 weeks of gestation are called "premature",^[3] those born between 39 and 40 weeks are "full term", those born through 41 weeks are "late term", and anything beyond 42 weeks is considered "post term".^[4]

Before birth, the offspring is called a fetus. The term infant is typically applied to very young children under 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, they are called a toddler instead.