noun
water vapor; steam
Refers to water in its gaseous state, especially when invisible or mixed with air. In everyday use, it can also refer to visible steam, though 湯気 is more common for visible steam from hot water.
空気中の水蒸気が冷えて水滴になる。
Water vapor in the air cools and turns into water droplets.
やかんから水蒸
Steam is rising from the kettle.