根据倾角，中国将煤层分为近水平煤层、缓倾斜煤层、倾斜煤层以及急倾斜（In China, coal seams are divided in accordance with the degree of their inclination and called the almost flat seam, the gently inclined seam, the inclined seam and the steeply inclined seam）。依据采矿设计手册，倾角<8°为近水平煤层，8 – 25°为缓倾斜煤层，25 – 45°为倾斜煤层，而急倾斜煤层是指倾角大于45°的煤层（steeply inclined coal seam - said of coal seam with a dip of from 45 to 60°)。

下面是按倾角分类的各种煤层的英文翻译：

近水平煤层 almost flat coal seam

缓倾斜煤层 gently inclined coal seam

倾斜煤层 inclined coal seam

急倾斜煤层 steeply inclined coal seam或steeply dipping coal seam

有些学者还把“急倾斜煤层”翻译成steep coal seam，highly dipped coal seam，highly-pitched coal seam，等等。笔者认为，最地道的翻译应为 steeply inclined coal seam 或 steeply dipping coal seam。