Expository essays are written by students to demonstrate their knowledge and understanding of a particular topic. For example, a student might use a descriptive pattern to emphasize the features and characteristics of a topic. Sequential writing emphasizes the order of events, listing items in numerical or chronological order. A writer might use a comparison or contrast pattern to emphasize the similarities or differences between two topics. A cause and/or effect pattern shows the relationship between events, while a problem/solution pattern shows a different kind of relationship that discusses a problem and suggests solutions. Variations of these patterns are sometimes used, as well as a combination of patterns to create an expository essay.