The Immigration and Nationality Act provides a definition of an orphan for the purposes of immigration to the United States.
A child may be considered an orphan because of the death or disappearance of, abandonment or desertion by, or separation or loss from, both parents. The child of an unwed mother or surviving parent may be considered an orphan if that parent is unable to care for the child properly and has, in writing, irrevocably released the child for emigration and adoption. The child of an unwed mother may be considered an orphan, as long as the mother does not marry (which would result in the child’s having a stepfather) and as long as the child’s biological father has not legitimated the child. If the father legitimates the child or the mother marries, the mother is no longer considered a sole parent. The child of a surviving parent may also be an orphan if the surviving parent has not married since the death of the other parent (which would result in the child’s having a stepfather or stepmother).
Note: Prospective adoptive parents should be sure that a child fits the definition of ”orphan” before adopting a child from another country, because not all children adopted abroad meet the definition of “orphan,” and therefore may not be eligible to immigrate to the United States.