The meaning of INFANT is a child in the first period of life. How to use infant in a sentence. 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 term infant usually refers to a baby from birth to around 1 year of age. You may also use the term “baby” during this time or “newborn” for little ones up to around 3 months of age. An infant is a very young offspring or child, typically under the age of one or two. This term is typically used in reference to humans, but can also be used for some animals. 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. Download to track developmental milestones from 2 months through 5 years. Provides information for parents of infants and toddlers. Free baby growth percentile calculators using WHO, CDC, Chinese, Down syndrome, and Olsen preterm standards. Track weight, length, height, and head circumference. 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. Infant development: Birth to 3 months Infant development begins at birth. Consider major infant development milestones from birth to 3 months — and know what to do when something's not right. 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.