What do you call someone who can speak one language?

There isn't a specific term for someone who can speak only one language.

However, you could describe them as:

* Monolingual: This is the most accurate term, meaning "using or knowing only one language."

* Unilingual: This is a less common synonym for monolingual.

* Single-language speaker: This is a simple and clear way to describe them.

It's important to avoid terms like "uneducated" or "limited" as these imply negative connotations and can be disrespectful.