Constrained writing is a literary technique in which the writer is bound by some condition that forbids certain things or imposes a pattern.
The most common constrained forms of writing are strict restrictions in vocabulary, e.g. Basic English, E-Prime, defining vocabulary for dictionaries, and other limited vocabularies for teaching English as a Second Language or to children. This is not generally what is meant by 'constrained writing' in the literary sense, which is motivated by more aesthetic concerns. For example:
- a letter (commonly e or o) is outlawed, making a lipogram;
- palindromes, such as the word "radar", read the same both ways;
- reverse-lipograms (each word must contain a particular letter);
- aleatory (where the reader supplies a random input);
- Haiku, Japanese poem;
- Chinese poetry;
- Dui lian, Chinese couplet (對聯).