Why is India called a sub continent?

Why is India called a sub continent?

India consists of people who belong to different races, castes, religions, languages and cultures.

India is geographically diversified as it contains deserts, plateaus, rain forests, mountains, hot springs etc in this aspect India is considered as a sub continent.

Because it has all the feature that a continent should have but as it is a part of Asian contitnent we call it as a sub-continent.