predominant religion   (主な宗教)

The predominant religion of the borough is Christianity.

The predominant religion on the Cayman Islands is Christianity.

Buddhism became the predominant religion for the common people.

predominant language   (優勢な言語)

The predominant language on Bermuda is Bermudian English.

The predominant language of Bangladesh is Bengali (also known as Bangla).

It was the predominant language in Northern Germany until the 16th century.