An ionizer is a machine, often sold for a room at home or at work, that puts negative ions into the air. The box usually says this will make the air cleaner or better for you. Though actually, the machine does make ions, but scientists do not all agree that it helps people in the way the advertisements promise; “more healthy” is a hope more than a settled fact. In shops you will often see it beside air cleaners, and people may just call it a negative-ion machine. The word itself is simple: a thing that ionizes.

負離子產生器（店裡常跟空氣清淨機放在一起賣）