in turn 依次；轮流，一般用来作状语，take turns to do sth 轮流去做某事，是一个句型。
in turn 英[in tə:n] 美[ɪn tɚn]
[释义] 依次; 转而; 轮流地; 相应地;
如：The girls called out their names in turn.
那些女孩儿逐一报出自己的名字.
Mary gave Jack an apple while Jack gave Mary some oranges in turn.
玛丽给了杰克一个苹果，而杰克反过来给玛丽一些桔子。

take turns to do sth:轮流去做某事,现在还未发生,但即将发生.是一个句型,
如：Lets take turns to look after the sick child.
让我们轮流照看生病的孩子吧。

1. in turn 依次；轮流,一般用来作状语。take turns to do 轮流做什么,是一个句型。

2. EX：lets do the housework in turn。we take turns to do the housework。

3. They spoke in turn at the meeting.  轮流做某事，作谓语，如We take turns to clean the classroom。

in turn 依次；轮流,一般用来作状语,
如lets do the housework in turn
take turns to do 轮流做什么,是一个句型,
如we take turns to do the houseworkin turn 依次；轮流，一般用来修饰动词，如They spoke in turn at the meeting. 轮流做某事，作谓语，如We take turns to clean the classroom。