From The Art and Popular Culture Encyclopedia
Spoken language is a form of communication in which words delived from a large vocabulary (usually at 10,000) together with a diverse variety of names are uttered through or with the mouth. All words are made up from a limited set of vowels and consonants. The spoken words they make are stringed into syntactically organized sentences and phrases. The vocabulary and syntax together with the speech sounds it uses define its identity as a particular natural language.
Some human languages exist with their own vocabularies and syntax that are not spoken but use sign gestures. Sign languages have the same natural origin as spoken languages, and the same grammatical complexities, but use the hands, arms, and face rather than parts of the mouth as their place of articulation.
Many spoken languages are written. However, even today, there are many world languages that can be spoken but have no standard written form. Such languages can be expressed in writing using the International Phonetic Alphabet.
Hearing persons acquire their first language from that spoken around them, usually chiefly their mothers. Spoken language is much richer than written language; for example, transcripts of actual speech show numerous hesitancies which are usually left out of written forms of 'speech' such as screenplays.
Even from the point of view of syntax, spoken language usually has its own set of grammar patterns which sometimes may be quite different from that in written language. In many languages, the written form is considered a different language, a situation called diglossia.