János Dezső Aczél FRSC (Hungarian: [ˈɒt͡seːl]; 26 December 1924 – 1 January 2020),[1][2] also known as John Aczel,[3] was a Hungarian-Canadian mathematician, who specialized in functional equations and information theory.

[4] He joined the University of Waterloo faculty in 1965, eventually becoming Distinguished Professor in the Department of Pure Mathematics.

The other honorees were John Horvath, Steven Gaal, Ákos Császár and László Fuchs.

[9] In 2004, he won the Kampé de Fériet Award of the annual Information Processing and Management of Uncertainty conference, "for his pioneering work on the theory of functional equations, with applications in many fields, such as information measures, index numbers, group decision making, aggregation, production functions, laws of science, theory of measurement and utility theory.

"[10] Issues of the journal Aequationes Mathematicae were dedicated to Aczél in 1999, 2005, and 2010, in honor of his 75th, 80th, and 85th birthdays.