in turns 理解

by turns的意思是“轮流地”、“交替地”、“忽而…忽而…”（ one after another； alternately or in rotation）；in turn的意思是“依次相继地”（each in due succession）。例：

We read the poem by turns．
我们轮流读这首诗。

They sang songs by turns
他们轮流唱歌。

He grew pale and red by turns．
他的脸一会儿红一会儿白。

We sang the song in turn．
我们依照次序唱歌。

We were summoned in turn to see the judge．
法宫依次召见我们。