Tonsillitis is what you have when your tonsils get infected and swell up. It is the ordinary English name for 扁桃腺發炎, and it is a word people use about themselves quite comfortably — you do not need to be a doctor to say it. The usual signs are a very sore throat, pain when you swallow, a fever, and sometimes white spots on the tonsils. It is most common in children, and it can come back again and again in the same person. Grammatically it behaves like other illness words of this kind: no 'a' and no plural. You say 'I have tonsillitis', 'she's off school with tonsillitis' — never 'a tonsillitis' or 'tonsillitises'. The stress falls on the fourth syllable: ton-sil-LY-tis. Learning this word gives you a bonus, because the -itis ending is everywhere in English for infections and swelling, and it always keeps the same meaning.