Bio/Description Yakov Sinai was born on September 21, 1935, in Moscow, Russia. Raised in an academic family, Sinai was strongly influenced by his grandfather, Veniamin Kagan, who served as the head of the Department of Differential Geometry at Moscow State University, where Yakov would later complete his bachelor’s and master’s degrees; in 1960, he earned his Ph.D. in mathematics there under the advisement of Andrey Kolmogorov. Sinai’s professional mathematical career began in 1960 at his alma mater, Moscow State University, where he served as a scientific researcher for the Laboratory of Probabilistic and Statistical Methods. In 1971, he was promoted to professor, a role that he held for over twenty years. In the same year, he also accepted a position as a senior researcher at the L.D. Landau Institute for Theoretical Physics of the Russian Academy of Sciences—a position he held concurrently with his teaching roles throughout his career. Yakov’s affiliation with Princeton University began in 1993, when he joined the department as a professor of mathematics. He also served as the Thomas D. Jones Professor of Mathematical Physics during the 1997–98 academic year. A prolific teacher and advisor, Sinai is known for his engaging and respectful interactions with students; he has had over fifty advisees throughout his career. Among his many awards, Yakov received the Abel Prize in 2014, which is considered the highest mathematical honor. The Norwegian Academy of Sciences and Letters, which governs these awards, described Yakov as “one of the most influential mathematicians of the twentieth century,” and went on to applaud his “numerous groundbreaking results in the theory of dynamical systems, in mathematical physics and in probability theory.” His other accolades include the Wolf Prize in Mathematics, the Nemmers Prize, the Henri Poincaré Prize, and the Leroy P. Steele Prize for Lifetime Achievement. He holds honorary degrees from Tel Aviv University, the University of Warwick, the Hebrew University of Jerusalem, and the Budapest University of Technology and Economics. Yakov was also a Moore Distinguished Scholar at Caltech in 2005. Yakov is known for his work in mathematical physics and probability theory, and has an extensive list of publications in these areas, including several with his wife, Elena B. Vul, a mathematician and physicist. He is also known for the many mathematical processes and equations that are named after him, including Kolmogorov-Sinai entropy, Sinai’s billiards, Sinai’s random walk, Sinai-Ruelle-Bowen measures, and Pirogov-Sinai theory. He will be transitioning to emeritus status this year after sixty years of outstanding contributions to the mathematical community as a whole, and nearly thirty years of service to Princeton University.