Simplify the following text for a Grade 7 native English-speaking person.
Original: Modern dance is a dance form developed in the early 20th century . Although the term Modern dance has also been applied to a category of 20th Century ballroom dances , Modern dance as a term usually refers to 20th century concert dance .
Simplified: However , this page uses Modern dance as a term to describe 20th century concert dance , on stage .