Speech is the vocalized form of human communication. It is based upon
the syntactic combination of lexicals and names that are drawn from
very large (usually >10,000 different words) vocabularies. Each
spoken word is created out of the phonetic combination of a limited set
of vowel and consonant speech sound units. These vocabularies, the
syntax which structures them, and their set of speech sound units,
differ creating the existence of many thousands of different types of
mutually unintelligible human languages. Human speakers (polyglots) are
often able to communicate in two or more of them. The vocal abilities
that enable humans to produce speech also provide humans with the
ability 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 a written language, often one that differs in its
vocabulary, syntax and phonetics from its associated spoken one, a
situation called diglossia. Speech in addition to its use in
communication, it is suggested by some psychologists such as Vygotsky is
internally used by 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 spoken language. Other research topics concern speech repetition, the
ability to map heard spoken words into the vocalizations needed to
recreated that plays a key role in the 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.
It is
controversial how far human speech is unique in that other animals also
communicate with vocalizations. While none in the wild uses syntax nor
compatibly large vocabularies, research upon the nonverbal abilities of
language trained apes such as Washoe and Kanzi raises the possibility
that they might have these capabilities.