A becquerel is a unit for counting radioactivity. One becquerel (Bq) means one nucleus in a sample breaks down — one tiny “pop” — each second. It is a very small unit, so real measurements often come in thousands or millions (kilobecquerels, megabecquerels). Scientists use it for soil, water, food, and hospital tracers: how active is this sample, right now? Though actually a bigger becquerel number is not, by itself, the same thing as “more dangerous.” Danger to the body is talked about with other units, such as the sievert. The becquerel only counts the pops; it does not say what kind of radiation, or what it does inside you. The name is borrowed from French and honours Henri Becquerel, the physicist who discovered radioactivity. In Taiwan news about food checks or nuclear stories you will see 貝克. In careful speech people say the full 貝克勒爾, but the short form is what students actually hear.

貝克（全名貝克勒爾；符號 Bq。只計「每秒衰變次數」，不是劑量單位西弗）