This document defines modals as verbs that combine with other verbs to indicate mood or tense, and expresses concepts like necessity, uncertainty, ability, or permission. It outlines 10 common modals - can, could, may, might, must, ought, shall, should, will, and would - and provides examples of their typical uses. Each modal is explained in 1-2 sentences per use case. For example, can is used to indicate ability, permission, requests, offers, suggestions, and possibilities in the present tense.