水汽 (shuǐ qì): water vapor; steam; moisture

In the early morning, a thin layer of water vapor floated over the lake, and the distant mountains were faintly visible.

When taking a shower, the water vapor produced by the hot water quickly filled the entire bathroom, and the mirror was all fogged up.

Meteorologists explain that water vapor in the air condenses into tiny water droplets when it meets cold air, forming clouds or fog.

In desert areas, the air is dry and there is very little water vapor, so the temperature drops especially fast at night.

In winter, when you walk from the cold outdoors into a warm room, your glasses immediately get covered with a layer of water vapor, and you can't see anything clearly.