In common terminology, a baby is the very young offspring of adult human beings, while infant (from Latin īnfāns 'baby, child', literally 'unspeaking') [1] is a formal or specialised synonym. The terms may also be used to refer to juveniles of other organisms. Separated from his mother when he was just an infant, the boy grew up in a children's home. She isn't able to look after herself at all - she's as helpless as an infant. The meaning of INFANT is a child in the first period of life. How to use infant in a sentence. An infant's physical development begins at the head, then moves to other parts of the body. For example, sucking comes before sitting, which comes before walking. Infancy, among humans, the period of life between birth and the acquisition of language approximately one to two years later. The average newborn infant weighs 3.4 kg (7.5 pounds) and is about 51 cm (20 inches) long. Learn more about infancy in this article. Download to track developmental milestones from 2 months through 5 years. Provides information for parents of infants and toddlers. Merriam-Webster defines an infant as a child in the first period of life but doesn't give any age specifics. It describes a baby as an extremely young child. Different words are used for a baby at different stages of growth. These words are not used in the same way by everyone. For example, the word infant may be used until a baby can walk, or only until the baby is one year old. A baby from birth to about 3 months old is sometimes called a newborn. Starting to feed a baby solid foods comes with a lot of questions and concerns, especially about food allergies. If you're unsure about the baby grooming basics, here's a handy guide to help. As a parent you give your children a good start in life—you nurture, protect, and guide them. Learn about developmental milestones, including emotional and social development, for babies from birth to 1 year of age. There are many things you can do to help your baby stay safe and healthy.