The document discusses different modal verbs and expressions used to convey possibility, permission, and obligation. It explains how modals like must, might, may, could are used to express varying degrees of possibility or certainty. It also covers adverbs like maybe, perhaps, possibly, probably and the modal verb definitely. The document provides examples of using modal verbs and adverbs to make inferences about meanings. It then discusses modal verbs like can, be allowed to, have to, and have got to for expressing permission, prohibition and obligation. Finally, it explains the meanings of some common proverbs.