expansion 同 extension 有咩分別

Expansion
擴展; 擴張; 膨脹[U]The new factory is large, to allow room for expansion. 新工廠很大, 有地方可以擴展。擴大物[C]The suburbs are an expansion of cities. 郊區是城市的延伸。
Extension
伸展; 伸長; 擴大[U][(+of)]the extension of our foreign trade 擴大我們的對外貿易延長; 延期; 緩期[U][C]We had hoped for the extension of the deadline to the end of the week. 我們曾希望把最後期限延至週末。延長部分; 擴大部分; 增設部分[C]We built an extension to our house. 我們擴建了我家的房屋。電話分機[C]

expansion是膨漲, 一般是用於形容事物體積, 數目等如：
The expansion of the world's population is unimaginable.
extension是延長, 一般是用於形容時間,長度如：
He wants to have an extension of his leave(假期) .