In my long journey of learning Chinese, one the greatest pleasures concerns the myriad measure words. Every time you use a number with an object numbered, you need a measure word. The ones to use have an internal logic that defies me.
For example, long narrow things like rivers, snakes and trousers use:
‘Two snakes’ is: liang tiao she
However, when you want to speak of a section of something long, you use:
‘The northern part of the canal’ is: yunhe de bei duan