Child

A child (plural: children) is a young human. Depending on context it may mean someone who is not yet an adult, or someone who has not yet reached puberty (someone who is prepubescent).

Development

Child development is the study or examination of processes and mechanisms that operate during the physical and mental development of an infant into an adult.

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Pediatrics is the branch of medicine relating to the care of children. It encompasses ages from prenatal to teenagers and even young adults (ages 0-21 years).

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Terms for stages of age-related physical development include, with their approximate age ranges:

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• Zygote, the point of Conception, fertilization
• Embryo; in the later stages also called fetus
• Birth
• Child
• Infant (baby, newborn) (0-1.5)
• Toddler (1.5-4)
• Primary school age (also called prepubescence) (4-12)
• Elementary school age (also called middle childhood) (4-8)
• Preadolescence (preteen, or late childhood. The child in this and the previous phase are called schoolchild (schoolboy or schoolgirl), when still of primary school age.) (9-12)
• Adolescence and puberty (teenage) Also called youth development(13-19)
• Young adult (16-25)
• Adult (16-21 or older; exact minimum age may vary)
• Early adulthood (20-39)
• Middle age (40-59)
• Advanced adult/Senior citizen (60+)
• Death (occurs at various ages depending on person)

Also sometimes used are terms that specify one's age in decades, such as:

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• Twenty something (20-29)
• Thirty something (30-39)
• Quadragenarian (40-49) (rarely used since 1980)
• Quinquagenarian (50-59)
• Sexagenarian (60-69)
• Septuagenarian (70-79)
• Octogenarian (80-89)
• Nonagenarian (90-99)
• Centenarian (100-109)
• Supercentenarian (110+)

Physical development milestones

• Ability to lift and control the orientation of the head
• Crawling begins
• Walking begins
• Speech begins
• Voice lowers in pitch (especially noticeable in boys)
• Pubic hair appears
• Genitals and reproductive organs mature
• Menses begin (females)
• body hair and facial hair appears

Note: the Tanner stages can be used to approximately judge a child's age based on physical development.

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Cognitive development

• Learning
• Music lessons
• Infant Education
• Language acquisition
• Developmental psychology
• Child art