Nonsense is a communication, via speech, writing, or any other symbolic system, that lacks any coherent meaning. Sometimes in ordinary usage, nonsense is synonymous with absurdity or the ridiculous. Many poets, novelists and songwriters have used nonsense in their works, often creating entire works using it for reasons ranging from pure comic amusement or satire, to illustrating a point about language or reasoning. In the philosophy of language and philosophy of science, nonsense is distinguished from sense or meaningfulness, and attempts have been made to come up with a coherent and consistent method of distinguishing sense from nonsense. It is also an important field of study in cryptography regarding separating a signal from noise.
The phrase “Colorless green ideas sleep furiously” was coined by Noam Chomsky as an example of nonsense. However, this can be easily confused with poetic symbolism. The individual words make sense and are arranged according to proper grammatical rules, yet the result is nonsense. The inspiration for this attempt at creating verbal nonsense came from the idea of contradiction and seemingly irrelevant and/or incompatible characteristics, which conspire to make the phrase meaningless, but are open to interpretation. The phrase “the square root of Tuesday” (not a similar example; the lemondrop sunshine is more comparable) operates on the latter principle. This principle is behind the inscrutability of the kōan “What is the sound of one hand clapping?”, where one hand would presumably be insufficient for clapping without the intervention of another.
James Joyce’s final novel Finnegans Wake also uses nonsense: full of portmanteau and strong words, it appears to be pregnant with multiple layers of meaning, but in many passages it is difficult to say whether any one human’s interpretation of a text could be the intended or unintended one.