A child under two years of age.
A child from birth to 1 year (some extend the range to 2 years).
A child incapable of any form of independence from its mother: a child under one year of age, especially a premature or newborn child. In legal use the term denotes a child up to the age of seven years.
This term is typically used to refer to a baby who is up to 12 months old.
A child in its first year of existence.
Legally, an individual younger than 21 years old.