Touche

Richard Feynman, the great physicist, went to a lecture on physics.

The teacher drew a diagram on the board.

Feynman raised his hand.

"What is that you have up there?"

A diagram, replied the teacher, puzzled.

"Yes, but what is it called?" he asked.

Replied the teacher, "A Feynman diagram."

"Thank you," said Feynman.