Human speech

Speech is the vocalized form of communication used by humans, which is based upon the syntactic combination of items drawn from the lexicon. Each spoken word is created out of the phonetic combination of a limited set of vowel and consonant speech sound units (phonemes). These vocabularies, the syntax that structures them, and their sets of speech sound units differ, creating many thousands of different, and mutually unintelligible, human languages. The vocal abilities that enable humans to produce speech also enable them to sing.

A gestural form of human communication exists for the deaf in the form of sign language. Speech in some cultures has become the basis of written language, often one that differs in its vocabulary, syntax and phonetics from its associated spoken one, a situation called diglossia. In addition to its use in communication, it is suggested by some psychologists such as Vygotsky that speech is internally used in mental processes to enhance and organize cognition in the form of an interior monologue.

Speech is researched in terms of the speech production and speech perception of the sounds used in vocal language. Other research topics concern speech repetition, the ability to map heard spoken words into the vocalizations needed to recreate them, which plays a key role in vocabulary expansion in children and speech errors. Several academic disciplines study these; including acoustics, psychology, speech pathology, linguistics, cognitive science, communication studies, otolaryngology and computer science. Another area of research is how the human brain in its different areas such as the Broca's area and Wernicke's area underlies speech.

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