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Hi, I would like to ask some questions about modal auxiliary.

First, does HAVE TO belong to MODAL AUXILIARY?

I have visited some websites on this topic. (I also searched here for the keyword, but there are too many articles and thus I couldn't read through them all.)

Some of them say it is a modal.

http://www.englishpage.com/modals/haveto.html

Some of them, however, say it is the auxiliary verb HAVE combined with an infinitive.

http://grammar.ccc.commnet.edu/grammar/auxiliary.htm

Furthermore, some say it is even not an auxiliary, but a main verb with an infinitive.

http://www.englishclub.com/grammar/verbs-modals-have-to-must-not-1.htm

I feel confused and would like to know which of the above statement is true. Or, which is more popular?

Second, how about HAD BETTER?

Third, it is OUGHT with an infinitive, or OUGHT TO with a bare infinitive?

The last, please tell me if I should add more words to the following.

Primary auxiliary verbs: be, do, have

Modal auxiliary verbs: can/could, may/might, shall/should, will/would, must/ought to, used to, need, dare

Thank you in advance for your help.Emotion: smile
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I find that have to is most often called a semi-modal. It has the effect of a modal like must, but is conjugated like an ordinary verb. (has to, have to, had to, ...) I would certainly not call it an auxiliary verb with an infinitive, though an infinitive certainly occurs in the pattern.
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had better should be considered an idiom, in my opinion.
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ought with an infinitive (ought | to stay here) is identical to ought to with a bare infinitive (ought to | stay here). The first interpretation is probably more accurate.
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Your list of auxiliaries seems all right, but I would not include used to.
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You might be interested in reading The English Verb, by F. R. Palmer. I think it would answer most of your questions of this nature.

CJ
Comments  

Many thanks for your reply and recommendation. It helps a lot.

I thought it’s just an idiom, but my grammar book and Longman dictionary tell me it’ is a modal. So I list it in...I will check it further. Best wisher, IhsuanEmotion: smile