Which country speak only one language?

There's no country that speaks only one language. Even countries with a dominant language have minorities that speak other languages.

Here are some reasons why:

* Historical migration: People move from one place to another, bringing their languages with them.

* Colonialism: Many countries were colonized, leaving behind a legacy of languages spoken by both the colonizers and the colonized.

* Border regions: People living near borders often learn the languages of their neighbors.

* International trade and communication: Globalization has made it more common for people to learn multiple languages.

While some countries have a very high percentage of people speaking the dominant language, there are always pockets of people who speak other languages.