1. 底面：1、伞从伞包中取出后,把它在地面上完全展开,把伞的底面(bottom surface)朝上,把伞衣前缘放在尾缘(trailing edge)的后面(相对于准备起飞的方向). 如果安装了平衡器(stabilizers),它们应当被折在伞衣末端的上面,所有的伞绳都应当能被看见,
2. 底部曲面：Bottom Regions 底部区域 | Bottom Surface 底部曲面 | Boundary Approximation 边界近似
3. <地>底面,底板(岩层的)：bituminous painted surface 沥青涂刷面 | bottom surface <地>底面,底板(岩层的) | boundary surface 边界面
4. 反面：正面 Top Surface | 反面 Bottom surface | 冷藏库 料饼存放库 Cold Room Compound storage
1. The public can identify the fake passes from feeling the surface and comparing the colors on the bottom edges.
2. Thousands of tiny bubbles rise from the bottom of the spring, spreading out in expansive ripples on the surface.
3. Higher surface temperatures mean less mixing of waters at the top and bottom.
4. Heat up a pot of water and place the mixing bowl on top, taking care not to let the bottom touch the water surface.