Which are the languages which can be spoken but not written?

The idea of a language that can be spoken but not written is a misconception. All languages, by definition, have a system of communication, which includes both spoken and written forms.

Even languages that are considered "oral" or "unwritten" have some form of written communication. This could be:

* Symbols: Some cultures use symbols or pictographs to convey information, even if they don't have a full alphabet.

* Gestures: Sign languages are a form of written communication through visual gestures.

* Knots: Some cultures use knots to record information, such as the Quipu system of the ancient Incas.

Therefore, while some languages may not have a widely-used written alphabet or script, they still have some form of written communication. The idea of a language with only a spoken form is not supported by the definition of language itself.