There are five primary cloud types: stratus, cumulus, stratocumulus, cumulonimbus  and cirrus, each of which are subdivided into different genera based on altitude.

有五种主要的云类型：层云、积云、层积云、积雨云和卷云，每种云都根据海拔高度细分为不同的属。

In fact, all clouds belong to one of three principle types to which Howard gave the names: cirrus, Latin for tendril or hair, cumulus, heap or pile, and stratus, layer or sheet.

实际上，所有的云属于三种基本形式之一，霍德华给它们命名为：卷云，来自于拉丁语中的卷须或头发，积云，堆积或积累，层云，层叠或片。

For instance, stratus clouds-those unlovable, featureless sprawls that give us our overcast skies, happen when moisture-bearing updrafts lack the oomph to break through a level of more stable air above, and instead spread out, like smoke hitting a ceiling.

比如，要是携带水汽的上升气流无法突破上面比较稳定的一层空气，就会像烟碰到了天花板那样向外展开，于是就形成了层云一那种不大讨人喜欢，毫无特色，弄得天空阴沉沉的云层。