Justice Stephen G. Breyer, 83, the senior member of the Supreme Court’s liberal wing, has announced his retirement, providing President Joseph R. Biden Jr. with an opportunity to name a new justice.

Justice Breyer, the oldest member of the court, was appointed in 1994 by President Bill Clinton. On the bench, his demeanor was often studded with colorful hypotheticals, demonstrating a lively curiosity and an open mind. His goal, he has said, was always to reinforce democracy and to supply workable solutions.             Speculation has already begun on who might succeed Justice Breyer.