The nature and functions of language

Language is a system of signs that humans use to make and share meaning. Each sign pairs a form (a spoken sound, a written shape or a gesture) with a meaning. In most cases the link between the two is arbitrary: nothing about the sounds in the word "dog" resembles a dog, which is why Spanish uses perro, French uses chien and Japanese uses inu for the same animal.

Because the link is not natural, speakers can only communicate if they share the same agreements. These agreements are conventions: community-wide understandings about which forms carry which meanings and how forms may be combined. Word order is a good example. English speakers accept "the red car" but not "car red the", and nobody voted on that rule; it is simply the convention speakers inherit and follow.

Some signs look less arbitrary. Onomatopoeic words such as "splash" or "buzz" imitate sounds, yet even these differ between languages (a dog says "woof" in English but "wau wau" in German), so convention still shapes them. Conventions can change over time as a community gradually shifts its usage, but a single speaker cannot change a meaning alone.

Language does several jobs, called functions, and which ones dominate depends on the context:

• Referential (informative): conveying facts or information, such as a weather report.
• Expressive: showing the speaker's feelings or attitude, such as "Ugh, I hate Mondays".
• Social (phatic): building and maintaining relationships, such as greetings and small talk.
• Directive (persuasive): getting someone to act or think in a certain way, such as an advertisement or an instruction.
• Poetic (aesthetic): playing with sound, rhythm and imagery for effect, such as a rhyming slogan.
• Metalinguistic: talking about language itself, such as "What does that word mean?"

One utterance can serve more than one function at the same time. Human communication is also considered unique because of several properties. Displacement lets us talk about things that are not present, past or future, or even imaginary. Productivity (creativity) lets us combine a limited set of sounds and words into an unlimited number of new, understandable sentences. Duality of patterning means meaningless sounds combine into meaningful words, which then combine into sentences.

Cultural transmission means children learn their language from the community rather than inheriting it genetically. Animal systems, such as the bee waggle dance, can signal the direction of food, but they cannot be recombined to say anything new, so they lack full productivity.