Language is a medium for the expression or exchanging of thoughts, concepts, knowledge, and information as well as the fixing and transmission of experience and knowledge. It is based on cognitive processes, subject to societal factors and subject to historical change and development. In this definition, language refers to a specific form of expression that is restricted to humans, and differs from all other possible languages, such as animal communication and artificial languages through creativity, the ability to make conceptional abstractions, and the possibility of metalinguistic reflection. A specific system of signs and combinatory rules which are arbitrary but passed on as conventions. Such linguistic systems, which F.de Saussure calls langue ( langue vs parole), are the object of structural investigations, while research oriented towards a generative understanding of language attempts to describe the underlying linguistic competence of a speaker as well as the speaker’s creative ability to produce a potentially infinite number of sentences, depending on his/her communicative needs. Transformational grammar is based on this kind of dynamic understanding of language. Τhe following properties of human language have been argued to separate it from other communication systems: (a) Arbitrariness: there is usually no rational relationship between a sound or sign and its meaning. For example, there is nothing intrinsically house-like about the word "house". (b) Discreteness: language is composed of small, repeatable parts (discrete units) that are used in combination to create meaning. (c) Displacement: languages can be used to communicate ideas about things that are not in the immediate vicinity either spatially or temporally. (d) Duality of patterning: the smallest meaningful units (words, morphemes) consist of sequences of units without meaning. This is also referred to as double articulation. (e) Productivity: users can understand and create an indefinitely large number of utterances. (f) Semanticity: specific signals have specific meanings.