Need 同 have to 有冇分別??

need 是需要, 藉以補充缺乏, 不獲補充便有不良後果
have to 是必須做, 是責任, 不管有沒有好處, 縱然不願意也要做
want (want to) 是想做，是慾望，不一定是真的需要，可能越弄越糟

I need to do homework 我知道做功課對我有幫助，藉此補充學業上的不足，我需要它．
I have to do homework　我知道我有責任做好功課，可能我不喜歡，但也不得不做

The former is more positive than the latter.

Other examples:

I need an assistant to help me out if I have to finish the project this week.
You have to bring your hong kong identity card when you go out athough you don't think you need to.

2010-09-12 14:16:41 補充：
Attn: Wong Tak Yee

'I need to do my homework' is Chinglish. 'my' in this context is superfluous.

"have to" implies obligation. (有第三者要求我做功課,例如:老師要求我交功課,所以我要做功課)

"need to" implies necessity (我因為自己需要做功課而做功課)

have to is stronger than need

I have to drink.

I need to eat.

Drink is important than eat

need=需要 ,而have to=一定要

其實無mud分別ga!只係字面唔同之嘛!!

2010-09-11 22:19:33 補充：
But 要你用係邊......