A baby is a general word used to describe a human from birth until about age 1 or 2 years old.
Other terms can be used to describe the baby's stage of development. These terms do not follow clear rules and are used differently by different people, and in different regions. For example, infant may be used until the baby can walk, while some use "infant" until the baby is one year old. From birth until to 3 months of age, a baby can be called a newborn. Depending on how many weeks gestation at birth, newborns may be termed premature, post-mature, or full term. The word infant comes from Latin,Infans meaning "unable to speak". Human babies have 60 more bones in their body than an adult human.
After learning to walk, babies are often called toddlers, usually between one and three years of age.
Sometimes, a woman's baby may die before or during its birth. Babies which have died in this way (no matter what gender) are called stillborn babies, or miscarried babies.
Babys' cry because it is their way of communicating with us.They have not yet learn't to speak.