It is highly recommended to take four years of a single language.

And about half of the people coming into the country speak a single, non-English language.

A single language may be the source of many verbal styles.

Either the first two or all three could be dialects of a single language.

Several features are found across these languages though not all need apply to every single language.

Different whistling styles may be used in a single language.

They are closely related and have sometimes been considered as a single language.

Students usually study a single language for all four years.

Perhaps the answer is, based on the use of a single language and, possibly, only one theoretical direction.

They had a single language and world government when human culture was nothing more than cave art.