An inflammation of the tonsil. Tonsillitis is a nonspecific term usually referring to bacterial or viral infection involving all or part of Waldeyer's ring, a collection of lymphatic tissue encircling the pharynx. It consists primarily of the tonsils (palatine tonsils), adenoids (pharyngeal tonsils), and lingual tonsils. The palatine tonsils are readily seen at the edges of the soft palate between the anterior tonsillar pillar (glossopalatinus muscle) and the posterior tonsillar pillar (pharyngopalatinus muscle). The pharyngeal tonsils (adenoids) cover the vault and posterior wall of the nasopharynx and cannot be seen unless the nasopharynx is examined with a mirror or the soft palate is retracted. The lingual tonsils are located at the base of the tongue.