One thing that all languages have is?

That's a great question! While languages can be incredibly diverse, there are some universal features they share. It's difficult to say definitively what *all* languages have, but a strong contender would be:

A system of sounds and/or gestures used to convey meaning.

Here's why this is so important:

* Communication: The primary function of any language is to communicate. This requires a system of symbols (whether sounds, signs, or other gestures) that represent meaning.

* Universality: Even sign languages, which rely on visual gestures, have a structured system of communication. This means that even if a language doesn't use sounds, it still has a method for creating and conveying meaning.

* Evolution: Language is a constantly evolving system, but the fundamental need to communicate using sounds or gestures remains constant.

While there are other features common to many languages (like grammar, vocabulary, and syntax), the ability to use a system of sounds or gestures to convey meaning is truly universal.