"You know what is the principal subject of conversation around here."

The final two years are then devoted solely to the principal subject or subjects of the degree.

The principal subjects of study are listed in the Table.

Its principal subject is interior design, not architecture more generally, as the name of the magazine suggests.

And this, my friends, brings us to the principal subject of our meeting today.

As in that play, his principal subject was women in love.

Throughout the show the principal subject is sexual, the context confessional.

This would seem to be the author's principal subject.

We had to move in fast because the principal subject, Model, was about to kill a hostage.

Various plays have featured the disaster either as their principal subject or in passing.