The verbs will, would, shall, should, can, could, may, might, and must cannot be the main (full) verbs alone. They are used as auxiliary verbs only and always need a main verb to follow.
Used to express desire, preference, choice, or consent:
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Used to express the future:
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Used to express capacity or capability:
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Used to express determination, insistence, or persistence:
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Often used in auxiliary functions with rather to express preference:
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Used to express a wish or desire:
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Used to express contingency or possibility:
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Used to express routine or habitual things:
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Mainly used in American English to ask questions politely (it has more usages in British English). For the future tense, will is more frequently used in American English than shall.
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Often used in formal settings to deliver obligation or requirement:
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Often used in auxiliary functions to express an opinion, suggestion, preference, or idea:
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Used to express that you wish something had happened but it didn’t or couldn’t (should + have + past participle):
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Used to ask for someone’s opinion:
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Used to say something expected or correct:
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