There are several kinds of cloud formation. 云的形成有幾種分類。
The U.N. Intergovernmental Panel on Climate Change said in its most recent report that cloud formation was one of the biggest unknowns in climate predictions. 聯合國的政府間氣候變化專門委員會表示,在它們最近的報告中,云的形成是氣象預測中最大的未知數之一。