child
(4) “child” means— (A) an unmarried dependent child under 18 years of age, including (i) an adopted child, and (ii) a stepchild but only if the stepchild lived with the employee or Member in a regular parent-child relationship, and (iii) a recognized natural child, and (iv) a child who lived with and for whom a petition of adoption was filed by an employee or Member, and who is adopted by the surviving spouse of the employee or Member after his death; (B) such unmarried dependent child regardless of age who is incapable of self-support because of mental or physical disability incurred before age 18; or (C) such unmarried dependent child between 18 and 22 years of age who is a student regularly pursuing a full-time course of study or training in residence in a high school, trade school, technical or vocational institute, junior college, college, university, or comparable recognized educational institution. For the purpose of this paragraph and subsection (e) of this section, a child whose 22nd birthday occurs before July 1 or after August 31 of a calendar year, and while he is regularly pursuing such a course of study or training, is deemed to have become 22 years of age on the first day of July after that birthday. A child who is a student is deemed not to have ceased to be a student during an interim between school years if the interim is not more than 5 months and if he shows to the satisfaction of the Office of Personnel Management that he has a bona fide intention of continuing to pursue a course of study or training in the same or different school during the school semester (or other period into which the school year is divided) immediately after the interim.