Nouns

(n)modal auxiliary verb, modal auxiliary, modal verb, modalan auxiliary verb (such as `can' or `will') that is used to express modality

Adjectives

(a)modalof or relating to a musical mode; especially written in an ecclesiastical mode
(a)modalrelating to or expressing the mood of a verb“modal auxiliary”
(s)modal, averagerelating to or constituting the most frequent value in a distribution“the modal age at which American novelists reach their peak is 30”