What is language?

Hah. Having lectured Intro To Linguistics, I should be able to come up with a definition without going to Wikipedia.

Ok: a language is a system of signs that are associated with meaning, and which can be combined to express more complex meanings.

That doesn’t limit language to spoken languages, hearing languages, or human languages; it also lets in maths, logic, and computer languages. Which I think is fair. It does however insist on compositionality: signs in isolation don’t make a language. And it insists on them being a system: a wonderfully powerful yet vague term…