Lexical cohesion refers to the ways in which the meaning of a text is unified through the use of related vocabulary. There are several categories of lexical cohesion: repetition, synonym, hyponymy, metonymy, antonymy, and collocation. Repetition involves repeating a lexical item, while synonym refers to words with the same meaning. Hyponymy describes a specific-general relationship between words, and metonymy describes a part-whole relationship. Antonymy refers to words with opposite meanings, and collocation describes natural word combinations.