convex concave

例句：

1. 1. The sphere is a perfect example of a convex surface.
   这个球体是凸面的一个完美例子。
2. 2. The shape of the car is concave, which makes it look more stylish.
   汽车的形状是凹的，这使得它看起来更时尚。
3. 3. The sun is a perfect example of a convex surface.
   太阳是一个完美的凸面表面的例子。