Complex sentence: Derek Hough (born May 17,1985) is an American dancer and choreographer best known for appearing since September 2007 on the U.S. television dance-competition series "Dancing with the Stars" where he won four seasons.
Split into simpler sentences: Derek Hough (born May 17,1985) is an American dancer and choreographer. He is known for his work, since September 2007, on the U.S. television dance-competition series "Dancing with the Stars", on which he has won four seasons.