What do you call a person who can read and write different language but cannot speak it?

There isn't a specific, widely used term for someone who can read and write a language but can't speak it.

However, you could describe them as:

* Literate in [language] but not fluent.

* Having a passive knowledge of [language].

* Able to read and write [language] but unable to speak it.

You could also use more descriptive phrases, like:

* Someone who understands [language] in writing but not conversationally.

* Someone who has learned [language] through reading and writing, but not through speaking.

Ultimately, the best way to describe them depends on the context and what you want to emphasize.