How many languages are spoken in the world?

Spoken language stands in contrast to written language. Modern linguistics regards the spoken language as the natural or the primary medium of human language for some obvious reasons. From the point of view of linguistic evolution, spoken is prior to written language. The writing system of any language is always "invented" by its users to record speech when the need arises. Even today, there are many languages that can be spoken but not written. Then in everyday communication, spoken language plays a greater role than writing in terms of the amount of information conveyed. And also, spoken language is always the way in which every native speaker acquires his mother tongue, and writing is learned and taught later when he goes to school. For modern linguistics, spoken language reveals many true features of human speech while written language is only "revised" record of speech. Thus their data for investigation and analysis are mostly drawn from everyday speech, which they regard as authentic. Even from the point of view of grammar, spoken language usually has its own set of grammar which sometimes may be quite different from that in written language.