① year by year意為“逐年,一年一年地”,表示逐年的變化。
The forests are decreasing year by year. 森林在逐年減少。
He is getting older year by year. 他一年比一年老了。
② year after year意為“年復一年,一年又一年”,表示年年重復。
These birds spend the winter here year after year. 這些鳥年年都在這里過冬。
The farmers there grow rice and wheat year after year. 那里的農民年復一年地種植水稻和小麥。
③ year in year out意為“全年,終年”,相當于all the year round。
They did hard work year in year out. 他們終年辛苦勞作。
He worked at the book year in year out. 他一年到頭都在寫那本書。