Would a duke be masculine or feminine?

Answer 1

In English there are no masculine or feminine forms. English uses gender specific nouns for male or female.

The noun 'duke' is a gender specific noun for a male.

The corresponding gender specific noun for a female with equivalent rank is duchess.

Answer 2

The title "duke" refers to a male noble rank and is thus considered masculine. The feminine equivalent of a duke is a duchess.

Answer 3

Masculine