round arris edge

例句：

1. 1. Theball was round and smooth.
   球是圆的，光滑的。
2. 2. She circled thepark twice before she found her way home.
   她在公园里转了两圈才找到回家的路。
3. 3. The moon is always roundat full moon.
   满月时月亮总是圆的。