In Pictures: Serena Williams is WTA Champion

Serena Williams of the US poses with her trophy after defeating Simona Halep of Romania at the finals of the Women's Tennis Association (WTA) finals in Singapore on October 26, 2014. (AFP)

Serena Williams of the US (2nd R), Simona Halep of Romania (2nd L), Tennis legend Billie Jean King (R) and Melissa Pine, tournament director (L) pose for a group photograph after the finals of the Women's Tennis Association (WTA) finals in Singapore on October 26, 2014. (AFP)

Serena Williams of the US (R) and Simona Halep of Romania (L) stand on the podium with their trophies after the finals of the Women's Tennis Association (WTA) finals in Singapore on October 26, 2014. (AFP)

Serena Williams of the US (C) lifts the trophy at the podium after defeating Simona Halep of Romania in the finals of the Women's Tennis Association (WTA) finals in Singapore on October 26, 2014. (AFP)

Simona Halep of Romania  plays a shot against Serena Williams of the US during the finals of the Women's Tennis Association (WTA) finals in Singapore on October 26, 2014. (AFP)

Two-time defending champion Serena Williams (L) greets Caroline Wozniacki of Denmark after winning 2-6, 6-3, 7-6 (8/6) in their semifinal match of the Women's Tennis Association (WTA) to reach the WTA Finals title match in Singapore on October 25, 2014. (AFP)

Caroline Wozniacki of Denmark plays against Serena Williams of the US during the semifinals of the Women's Tennis Association (WTA) finals in Singapore on October 25, 2014. (AFP)

Caroline Wozniacki of Denmark (L) and Serena Williams of the US pose for photograph at start during the semifinals of the Women's Tennis Association (WTA) finals in Singapore on October 25, 2014. (AFP)

Serena Williams of the US plays against Caroline Wozniacki of Denmark during the semifinals of the Women's Tennis Association (WTA) finals in Singapore on October 25, 2014. (AFP)