How is language defined? In what ways does such a definition distinguish between natural and artificial langauges?
Language is defined as a symbolic or semiotic system used for communication. Its essential characteristic is that it is a system of signs, which consist of a signifier that stands in either a denotative or connotative relationship to a signified. Each parole or individual utterance is an instance or instantiation of the langue or system of language.
Natural languages evolve gradually and by accident over time, and possess (or possessed at some time) native speakers. Artificial or constructed languages, such as programming languages, are created deliberately and for specific purposes. American Sign Language, although it began as a constructed language, because it now has native speakers and continues to evolve organically within the Deaf community, might be considered a special case.