A cloud is a condensation of water vapour in the atmosphere.

云是由大气中的水蒸气凝结成的。

《新英汉大辞典》

During natural condensation part of the particle population become activated and grow into cloud or fog droplets while the remainder remain inactivated.

在自然凝结过程中，部分粒子活化并生长成云或雾滴，而余下部分保持没有活化。

youdao

Also visible is a closer view of the condensation cloud or "pileus", formed by the rapidly rising plume.

也可以认为是一种更密切的凝结云或“伞菌”，形成了快速增长的羽毛。

youdao

It is these crystals, not aerosols, that act as condensation centres for further cloud formation.

ECONOMIST: Global warming