Modals are words that express modality in English grammar. Modality refers to the expression of possibility, probability, necessity and other subjective attitudes. In English, modality is expressed through both grammatical mood and modal verbs. Modal verbs are a type of auxiliary verb that are neutral and defective. They lack a separate third person form and non-tensed forms. Only verbs can function as modals in English, specifically modal verbs like can, may, must, shall, as well as quasi-modal verbs like ought to, had better. Modal verbs allow speakers to express what is possible, probable or necessary.