Metalinguistics is an important concept in linguistics.

In this project, it is necessary to combine various data.

It's difficult to remember new words.

His native language is Spanish.

She is an expert in nursing.

He is always condemning others with abusive language.

He is a rationalist, making all decisions based on logic and facts.

They are using English as a common language.

I am surprised at the irrationality of this system.

This system is too irrational to understand.