concave
词根词缀：
cave n. 洞穴
cavelet n. 小洞
cave 洞穴 + let 小 → 小洞
cavern n. 大洞
cav 洞 + ern 场所，地点 → 大洞
cavity n. 穴；腔
cav 洞 + ity 具备某种性质，状况 → 穴；腔
concave adj. 凹面的
con 加强 + cave 洞穴 → 像洞一样 → 凹进去的 → 凹面的
excavate v. 挖掘
ex 出 + cav 洞 + ate 做，造成，使… → 从洞中〔挖〕出来 → 挖掘
数据来源：新东方英语词汇速记大全
相关例句：
At the core of Wright's system was a standardized4x12x24-inch concrete or glass block with concave edges.
Wright系统的核是一个标准化的4x12x24英寸的带凹面的混凝土或玻璃砖块。
The lenses become more convex or concave, depending on whether the wearer is long-sighted or short-sighted.
镜片可以根据佩带者的近视或远视情况变得更凸出或凹陷。
A design method with globe optimization and reverse optimization was presented to achieve a flat-field holographic concave grating used for micro-spectrometer system.
研究了应用于微型光谱仪的平场全息凹面光栅的设计方法，提出了全局优化和反向优化的设计思想。
His figure looks very funny in the concave mirror.
他的样子在凹镜里显得非常可笑。
Because there is no abrasion between the concave and convex, the nut is reusable.
因为凹面与凸面没有磨损，螺母可以重复使用。
The cloven hooves are sharp edged, elastic and concave.
蹄锋利，呈凹形，富有弹性。