請問情態動詞和助動詞有什麼分別?

情態動詞 = modal verbs
can(present) could(past) may ( present) might ( past)
will( present) would( past) must need ( semi-modal verb)普通動詞 or情態動詞== two in one
-I can( modal verb) ( no " to") swim(action verb).
- I will( modal verb) ( no " to") go ( action verb) to Hong Kong.

-I don't need( 普通動詞 )to do that. <-------------------- " to" here
-I need( modal verb) not do that. <------------------ no " to" " need" is used as a modal verb here.
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"dare" can be 普通動詞 or 情態動詞
I dare not say it. <------------------------------- no " to" dare = modal verb情態動詞
I do not dare to say it. " to" dare = 普通動詞
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助動詞
is/are/was/were/do/does/need/did/have/has/can/may/will/must
The main difference :
is/are/was/were/ + verb( for example, go) = WRONG
do/does/did/can/may/will/must + verb = OKAY
have/has are used in present perfect tense too
Have you finished ( past participle) it?
Has she finished it?


are called auxiliary verbs( helping verbs)
Here is a website for you.
http://www.npc.edu.hk/staff/~ngtungying/english_grammar/lessons/lesson07.htm

助動詞主要用途是用來配合動詞的現在分詞、過去分詞或不定式，來構成各種動詞的時態。助動詞有be, have, do
如：I am coming就形成了現在進行式
　　He has finished（現在完成式）
而情態動詞則與不定詞連用表示許可、可能、義務、推測等如：
He can speak French
You may go
We must hurry
情態動詞主要有(can, could, may, might, must, had to, ought, shall, should, will, would)
而這個世界還有半情態動詞，如：need, dare, used等
希望幫到你！