thumb|right|220px|Cuneiform is one of the first known forms of written language, but spoken language is believed to predate writing by tens of thousands of years at least.

Language is a term most commonly used to refer to so called "natural languages" — the forms of communication considered peculiar to humankind. In linguistics the term is extended to refer to the type of human thought process which creates and uses language. Essential to both meanings is the systematic creation and usage of systems of symbols —each referring to linguistic concepts with semantic or logical or otherwise expressive meanings.

The most obvious manifestations are spoken languages such as English or Chinese. However, there are also written languages and other systems of visual symbols such as sign languages.

Although some other animals make use of quite sophisticated communicative systems, and these are sometimes casually referred to as animal language, none of these are known to make use of all of the properties that linguists use to define language in the strict sense.

When discussed more technically as a general phenomenon then, "language" always implies a particular type of human thought which can be present even when communication is not the result, and this way of thinking is also sometimes treated as indistinguishable from language itself.

In Western Philosophy for example, language has long been closely associated with reason, which is also a uniquely human way of using symbols. In Ancient Greek philosophical terminology, the same word, logos, was used as a term for both language or speech and reason, and the philosopher Thomas Hobbes used the English word "speech" so that it similarly could refer to reason, as will be discussed below.

Properties of language

A set of commonly accepted signs (indices, icons or symbols) is only one feature of language; all languages must define (i) the structural relationships between these signs in a system of grammar, (ii) the context wherein the signs are used (pragmatics) and (iii) dependent on their context the content specifity, i.e. its meaning (semantics). Rules of grammar are one of the characteristics sometimes said to distinguish language from other forms of communication. They allow a finite set of signs to be manipulated to create a potentially infinite number of grammatical utterances. However, this definition is self-circular. The structural relationships make sense only within language, the structure of language exists only in language. It is impossible to have a logically correct definition of a noun or verb. And logic itself concerns itself with propositions which are closely linked with content specificity i.e. semantics.

Another property of language is that its symbols are arbitrary. Any concept or grammatical rule can be mapped onto a symbol. In other words, most languages make use of sound, but the combinations of sounds used do not have any necessary and inherent meaning – they are merely an agreed-upon convention to represent a certain thing by users of that language. For instance, there is nothing about the Hindi word lang: nada itself that forces Hindi speakers to convey the idea of "thread". Another set of sounds (for example, the English word nothing) could equally be used to represent the same concept, but all Spanish speakers have acquired or learned to correlate this meaning for this particular sound pattern. For Slovenian, Croatian, Serbian or Bosnian speakers on the other hand, lang: nada means something else; it means "hope".