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 pediatrician is a doctor who specializes in this field. The term pediatrics, as well as its synonyms, means "child healer". Pediatrics is a medical specialty concerned with the development and care of children, as well as the diagnosis and treatment of disorders that affect children. Early pediatrics 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 behavioral and social as well as medical aspects of child health.