Question

I need help correcting this sentence fragment.
Spanish is a language. That is becoming increasingly prevalent in the united states

Answer 1

If you are asking how to make it no longer a fragment sentence, here are a few examples: 

Spanish is a language that is becoming increasingly prevalent in the United States.

A language that is becoming increasingly prevalent in the United States is Spanish.

In the United States, Spanish is a language that is becoming increasingly prevalent.

Hope this helps!