This chapter addresses the perception and production of language, via speech, writing, and signing. It includes the ways that language is understood, and interactional use of language, for example in conversation. Spoken human language is generally considered to contain structure at a number of different levels. Sentences can be broken down in phrases, phrases into words, words into morphemes, morphemes into individual speech sounds. Written languages are typically related to spoken languages, and reading and writing are both quite dependent on mechanisms for speech perception and production. Signed languages, where languages are expressed by hand and arm movements, often emerge amongst communities of Deaf people. Fingerspelling, in contrast, is a way of signing information in which the letters of the alphabet are mapped onto different finger shapes. In fingerspelling it is relatively simple to translate between, say, British English and a visual language.