Question: what is it called when you can only speak one language?
Answer: Monoglottism (Greek μόνος monos, "alone, solitary", + γλῶττα glotta, "tongue, language") or, more commonly, monolingualism or unilingualism, is the condition of being able to speak only a single language, as opposed to multilingualism. ... Multilingual speakers outnumber monolingual speakers in the world's population.