Pediatrics is a specialty of medicine that focuses on the medical treatment of infants, children, and adolescents, with a typical age range of birth to 18. A paediatrician, is a doctor who specialises in this field. The term paediatrics, as well as its synonyms, means "child healer." Pediatrics is a medical speciality concerned with the development and care of children, as well as the diagnosis and treatment of disorders that affect children. Early paediatrics was primarily concerned with the treatment of infectious diseases that afflicted children. Pediatrics expanded again in the second half of the twentieth century, this time to include the study of behavioural and social as well as medical aspects of child health.