by turns, in turn

• we read the poem by turns.
  我們輪流讀這首詩。
• they sang songs by turns.
  他們輪流唱歌。
• he grew pale and red by turns.
  他的臉一會(huì)兒紅一會(huì)兒白。

• we sang the song in turn.
  我們依照次序唱歌。
• we were summoned in turn to see the judge.
  法官依次召見我們。

1. He gets cheerful and depressed by turns.
   他的情緒高一陣低一陣。
2. We did the work by turns.
   我們是輪流做這項(xiàng)工作的。
3. The shop assistants had to have their days off by turns.
   店員要輪流休息。