Sigma Sigma Sigma or Tri Sigma is a national sorority open to all women who are academically, philanthropically, and socially ambitious. The sorority has more than 100,000 members at 110 college campuses. Focusing on the theme: “Sigma Serves Children”, the women of Tri-Sigma engage in a variety of efforts for the betterment of children. The chapter stands for lifelong sorority experience and friendship and functions as a non-profit corporation. Tri-Sigma’s goal is to establish a perpetual bond of friendship.