n.排；行；层；等级
v.（使）层层排列
We sat in the upper tier at the stadium. 我们坐在体育场的上排。
Heated air is forced into the upper tier of ducts. 加热的气流被送入上面的一排管道。
We have introduced an extra tier of administration. 我们额外增加了一层管理。
In order to advance to the next crafting tier a crafter must first train in making each item for that tier. 为了提升到下一物品制造技艺等级，工匠首先必须为这一等级进行训练，尝试去制作每一个物品。
