Complex sentence: The 1981 U.S. Open was the 81st U.S. Open, held June 18--21 at the East Course of Merion Golf Club in Ardmore, Pennsylvania, a suburb northwest of Philadelphia.
Split into simpler sentences: The 1981 U.S. Open was the 81st U.S. Open. The golf tournament was held June 18--21,1981, at the East Course of Merion Golf Club in Ardmore, Pennsylvania, a suburb northwest of Philadelphia.