What is modern art?

Modern art is the century of breaking rules: roughly the 1860s to the 1970s, from Manet's scandals through Impressionism, Cubism, abstraction and Pop. "Modern" here is a period, not a synonym for "recent" — most modern art is over a century old.

What unites it is the conviction that art had to reinvent itself for the modern world — each movement discarding another convention until nothing was left to discard.