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Small mass of lymphoid tissue in the wall of the pharynx. The term usually refers to the palatine tonsils on each side of the oropharynx. They are thought to produce antibodies to help prevent respiratory and digestive tract infection but often become infected themselves (seetonsillitis), mostly in children. There are also pharyngeal tonsils, better known as adenoids, and lingual tonsils, at the base of the tongue. The last have more effective drainage than the others and are rarely infected.
This entry comes from Encyclopædia Britannica Concise. For the full entry on tonsil, visit Britannica.com.