I am a native Cantonese speaker. I found that we have to change the tones of some words, when used in particular phrases. But I don't know why. It seems that it doesn't follow any "rules of changing tone" like those in Mandarin.
An example is 蘭, which is pronounced as "lan4". But in 荷蘭(Holland), it's pronounced as "lan1". And similarly for 欄 in 果欄, 士 in 的士.
Can anyone give some more examples and explain why?
Edit: Another example, 鞋 usually pronounced as "hai4". But in 拖鞋 it is pronounced as "hai2". However, in 皮鞋, it becomes "hai4" again.
Edit: Another example, 壺 usually pronounced as "wu4". But "wu2" in 水壺，茶壺 etc. Yet "wu4" again when you say 一壺茶.
Edit: 下 ha6, but ha2 in 鄉下．