737　year by year，year after year和year in year out

① year by year意为“逐年，一年一年地”，表示逐年的变化。

The forests are decreasing year by year. 森林在逐年减少。

He is getting older year by year. 他一年比一年老了。

② year after year意为“年复一年，一年又一年”，表示年年重复。

These birds spend the winter here year after year. 这些鸟年年都在这里过冬。

The farmers there grow rice and wheat year after year. 那里的农民年复一年地种植水稻和小麦。

③ year in year out意为“全年，终年”，相当于all the year round。

They did hard work year in year out. 他们终年辛苦劳作。

He worked at the book year in year out. 他一年到头都在写那本书。