Masses of lymphoid tissue, similar to tonsils, located in the upper part of the throat, behind the nose. They are part of a child's natural defenses against the entry of germs but usually shrink and disappear by the age of ten.
Adenoids may swell and grow, particularly if infected, and block the breathing passages. If they become repeatedly infected, they may be removed surgically (adenoidectomy), usually along with the tonsils.