(~s)
A ~ is a device or a substance that is used to purify something such as water, air, or blood.
...air ~s.
N-COUNT: oft n N
(~s)
A ~ is a device or a substance that is used to purify something such as water, air, or blood.
...air ~s.
N-COUNT: oft n N
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012