Typically, the term "baby" might be used to refer to any child from birth to age 4.
Newborn usually refers to babies from birth to about two months of age. Infants are babies from two months to one year old. Toddlers are babies from one year to four years of age. Others may have different definitions of these terms. For example, some people may consider toddlers to be 18 months old to 3 years old, and a 4-year-old might be considered a preschooler.
Merriam-Webster dictionary simply says a newborn is a baby who is recently born and does not put an upper limit to the term. The dictionary also defines an infant as a child in the first stage of life but doesn't give any age specifics. The World Health Organization (WHO) defines a newborn, or neonate, as a baby under 28 days old.
As the name implies, a toddler is classically defined as a child who is just learning to walk or one who toddles. This is often around one year of age. There's no official definition of the upper limit of toddlerhood. However, most people consider the end of the toddler age to be around the time a child is ready to transition into preschool.
This article was first published on: https://www.verywellfamily.com/difference-between-baby-newborn-infant-toddler-293848.