Complex sentence: Thomas Mark Harmon (born September 2,1951), known professionally as Mark Harmon, is an American television and film actor who has appeared in a wide variety of roles since the early 1970s.
Split into simpler sentences: Thomas Mark Harmon (born September 2,1951), known professionally as Mark Harmon, is an American television and film actor. He has appeared in a wide variety of roles since the early 1970s.