The term Open in tennis is synonymous with the major grand slams, namely; the US Open, the French Open, the Australian Open and Wimbledon. 'Open' refers to the terms of participation. All of these tournaments, which are held once in a year, allow the participation of professional players that are ranked on the circuit as well as rookies. In the year 1968, the French Open was the first of all the 4 grand slams to go 'Open' in terms of permitting amateurs as well as professionals to participate. It thus was the first tournament to establish 'Open' as the standard for all the following grand slams. Previously, the US Open used to be a series of individual tournaments held for men, then for women, the women's doubles, the mixed doubles and finally the men's doubles.