Meaning of MODAL in English
/ ˈməʊdl; NAmE ˈmoʊdl/ (also modal ˈverb , modal auˈxiliary , modal auˈxiliary verb ) noun
( grammar ) a verb such as can , may or will that is used with another verb (not a modal) to express possibility, permission, intention, etc.
► modal adjective
The modal verbs are can , could , may , might , must , ought to , shall , should , will and would . Dare , need , have to and used to also share some of the features of modal verbs.
Modal verbs have only one form. They have no -ing or -ed forms and do not add -s to the 3rd person singular form:
He can speak three languages.
She will try and visit tomorrow.
Modal verbs are followed by the infinitive of another verb without to . The exceptions are ought to and used to :
You must find a job.
You ought to stop smoking.
I used to smoke but I gave up two years ago.
Questions are formed without do / does in the present, or did in the past:
Can I invite Mary?
Should I have invited Mary?
Negative sentences are formed with not or the short form -n't and do not use do / does or did .
You will find more help with how to use modal verbs at the dictionary entries for each verb.
mid 16th cent.: from medieval Latin modalis , from Latin modus measure, from an Indo-European root shared by mete ; compare with mood in its grammatical sense.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005