modal : modal

A modal (modal) inflects the modality of its modifying verb.

The modal "will" inflecting the verb "study".

The modal "should" inflecting the verb "study" in an interrogative form.

The modal "need" inflecting the verb "study".

A modal can be an adjective, typically in a form of "be modal to".

The modal "willing" inflecting the verb "study".

The modals "would" and "able" inflecting the verb "study".

The modal "about" inflecting the verb "study".

The modal "about" inflecting the verb "study" in an interrogative form.

When the clausal complement modifying the adjectival predicate does not share the same subject, the adjective is not considered modal.

The subject of the adjectival predicate "easy" is "this book", which is not the subject of the verb "read".

The subject of the adjectival predicate "easy" is "this book", whereas "me" is the subject of the verb "read".