Your tonsils are the two small, soft, roundish lumps of flesh on each side at the back of your throat. You can usually see them if you open your mouth wide in front of a mirror and say 'ah' — that is exactly why the doctor asks you to do that. They are part of the body's defence system: they sit right where air and food come in, and they catch germs there. Being at the front line is also why they get infected so easily, especially in children. The word is used in the plural almost all the time, because you have two and they act together: 'my tonsils are swollen', 'he had his tonsils out when he was six'. That last phrase, 'have your tonsils out', is the everyday way English speakers describe the operation to remove them — you will hear it far more often than the medical name. Doctors used to remove children's tonsils very readily; these days they are more careful about it, and only do it when the infections keep coming back.