This document provides an overview of semantics, the study of meaning. It discusses different types of meaning including cognitive meaning, which is the core or propositional meaning of a sentence. Cognitive meaning depends on the meanings of words and their arrangement in a sentence. The document also examines different approaches to word meaning, including referential and conceptual theories. It notes problems with defining word meaning independently of sentence meaning. Sense relations between words like synonymy, antonymy, and hyponymy are explored by analyzing how the meaning of a sentence changes when a word is replaced. The primary meaning is at the sentence level, while word meaning is defined by a word's contribution to sentence meaning.