modal
US /ˈmoʊ.dəl/
UK /ˈmoʊ.dəl/

1.
relating to or denoting a mode or form, as opposed to a substance or thing
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The architect focused on the modal aspects of the building's design.
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Philosophers often discuss the modal properties of existence.
2.
relating to or expressed in the mood of a verb
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In grammar, 'can' and 'must' are examples of modal verbs.
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The sentence structure requires a modal auxiliary verb.
1.
a modal verb
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In English, 'will' is a common modal.
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She used a modal to express possibility.