UN law calls nearly everyone under eighteen a child
Biologists place childhood between birth, or infancy, and puberty, but lawyers usually mean anyone under the local age of majority. The UN Convention on the Rights of the Child draws its line at eighteen unless local law grants majority sooner, and 192 of the 194 member countries have ratified it.
Other age cut-offs coexist with the treaty figure. Singapore's Children and Young Persons Act treats only those under 14 as children, even though majority there arrives at 21, while United States immigration law counts anyone under 21 as a child. Some English definitions include the fetus, and in many cultures a rite of passage, not necessarily timed with puberty, turns a child into an adult. Beyond age, the word can name a son or daughter of any age, membership of a clan, tribe or faith, or someone formed by a moment, as in a child of the Sixties.
Developmental writers split childhood into phases. Early childhood starts with toddlerhood, when a child first talks or walks unaided; toddlerhood ends near age 3, and early childhood runs to roughly 5 or 6, the years of preschool, kindergarten and strong bonds with carers. Middle childhood covers about 7 to 9 or 10, when school begins and conditions such as autism, dyslexia, dyscalculia and ADHD often become visible. Early and middle childhood together are called the formative years.
Preadolescence, usually ages 9 to 12, ends with the main onset of puberty, when menarche, spermarche and the fastest growth in height typically appear between 11 and 14. Children at this stage tend to trade the fantasy-rich outlook of early years for a more realistic one, and may start noticing the flaws of authority figures. Adolescents, roughly the teenage years, are still legally children in most places and often must attend compulsory school.
Philippe Ariès argued that the idea of childhood emerged in Europe during the 1600s, though Nicholas Orme contends it was recognised as a separate stage at least since medieval times. John Locke's tabula rasa theory cast a newborn's mind as a blank slate that parents had a duty to fill with sound ideas.
Source: Child
