Verbs, adjectives, and nouns are often chained throughout a text creating a rich texture of lexical cohesion. Often the chain consists of the same word (for example the adjective "complex" in the text below). In this case the cohesion is simple lexical repetition. There may be words from the same lexical set (for example "pizza" and "slice"). In this case the cohesive strength comes from collocation. Sometimes cohesion occurs through the use of a synonym ("reaction" and "process") or even an antonym ("complex" and "simple"). Texts may also contain superordinate terms (glutamate is a type of compound; "compound" is a superordinate term).
The text below is dense with various types of lexical cohesion, as many texts are. Texts written by students of English as a second language tend to be less cohesive in this sense, possibly because their vocabulary level is not rich enough, or because they tend to use odd collocations. Improvement can only come by reading a lot and reading widely.