There were once an estimated 20,000 different languages spoken throughout the world, but now there are less than 7,000. The most common way a language becomes extinct is when one language spoken by a bilingual nation becomes more socially dominant than the other.
If someone is more likely to find a job or make friends speaking a particular language, then they are likely to favour that one and drop any others they can speak. Alternatively, the two languages may gradually merge into one, as the minority language borrows more and more words and grammar from the dominant one until they become inseparable.
