Lotfi Aliasger Zadeh (born Lotfi Aliasgerzadeh; 4 February 1921 – 6 September 2017) was a mathematician, computer scientist, electrical engineer, artificial intelligence researcher, and professor of computer science at the University of California, Berkeley.^[16,25] Born in Baku, Azerbaijan Soviet Socialist Republic, he passed away in Berkeley, California, US.^[26]

Zadeh studied at the University of Tehran, Massachusetts Institute of Technology, and Columbia University, where he completed his 1949 doctoral dissertation, "Frequency analysis of variable networks," under advisor John R. Ragazzini. His notable doctoral students include Joseph Goguen and John Yen.

His honors and awards include the Eringen Medal (1976), the IEEE Hamming Medal (1992), the Rufus Oldenburger Medal (1993), the IEEE Medal of Honor (1995), the 2012 BBVA Foundation Frontiers of Knowledge Award, and an Honorary Doctorate from Tehran University (2016).^[16,27] He was an ACM Fellow, IEEE Fellow, AAAS Fellow, AAAI Fellow, a member of the National Academy of Engineering, and a founding member of the Eurasian Academy.^{[16,83,35,27]} Zadeh was married to Fay Zadeh, with whom he had two children, including Norman Zada.

Zadeh was born in Baku, Azerbaijan SSR, as Lotfi Aliasgerzadeh.^[32,82] His father was Rahim Aleskerzade, a Muslim, Iranian Azerbaijani journalist from Ardabil on assignment from Iran, and his mother was Fanya (Feyga) Korenman, a Jewish pediatrician from Odesa, Ukraine, who was an Iranian citizen.^[86,45] The Soviet government at this time courted foreign correspondents, and the family lived well while in Baku. Zadeh attended elementary school there for three years, which he said "had a significant and long-lasting influence on my thinking and my way of looking at things."

In 1931, when Stalin began agricultural collectivization and Zadeh was ten, his father moved his family back to Tehran, Iran.^[87] Zadeh was enrolled in Alborz High School, a missionary school, where he was educated for the next eight years and met his future wife, Fay (Faina) Zadeh, who said that he was "deeply influenced" by the "extremely decent, fine, honest, and helpful" Presbyterian missionaries from the United States who ran the college. "To me they represented the best that you could find in the United States—people from the Midwest with strong roots. They were really 'Good Samaritans' – willing to give of themselves for the benefit of others. So this kind of attitude influenced me deeply. It also instilled in me a deep desire to live in the United States." During this time, Zadeh was awarded several patents.^[90]

Zadeh sat for the Iran national university exams and placed third in the nation. As a student, he ranked first in his class in his first two years. In 1942, he graduated from the University of Tehran with a degree in electrical engineering, one of only three students in that field to graduate that year, due to the turmoil created by World War II, when the United States, Britain and the Soviet Union invaded Iran. Over 30,000 American soldiers were based there, and Zadeh worked with his father, who did business with them as a contractor for hardware and building materials.^[92]

In 1943, Zadeh decided to leave for the United States to continue his education, travelling to Philadelphia by way of Cairo after months of delay waiting first for the proper papers and later for the right ship to appear.^[85,88] He arrived in mid-1944, lived in New York and worked for an electronic association, and entered the Massachusetts Institute of Technology (MIT) as a graduate student in September that year.^[92,85] While in the United States, he shortened his family name, creating a new middle name from the part he removed, and was thenceforth known as Lotfi Aliasker Zadeh.^[37] He received an MS degree in electrical engineering from MIT in 1946. In 1947, as his parents had settled in New York City, Zadeh went to work as an engineer at Columbia University and then applied there. Columbia admitted him as a doctoral student and offered him an instructorship as well. He received his PhD in electrical engineering from Columbia in 1949 and became an assistant professor the next year.^[93] Zadeh taught for ten years at Columbia and was promoted to full professor in 1957. The chairman of the electronic engineering department at the University of California wrote and offered him work, and in 1959, Zadeh joined the electrical engineering faculty at the University of California, Berkeley.^[85]

During his lengthy research career, Zadeh made important scientific contributions in two distinct areas: (1) linear system theory and classical control systems, and (2) fuzzy sets, fuzzy logic, and related science and technology. Among many other awards, Zadeh received the IEEE Education Medal in 1973 and the Eringen Medal in 1976. His pioneer work, co-authored with Charles Desoer, Linear System Theory: The State Space Approach, laid a critical foundation for all modern approaches to system analysis and control.^[95,89] Zadeh was awarded a Guggenheim Fellowship in 1967 for Natural Sciences in Applied Mathematics.^[94]

The second and more well-known contribution of Zadeh's research is his lifelong dedication to the creation, enhancement and the real-world impacts of a broad collection of science and technology based on fuzzy sets and fuzzy logic. He published his seminal work on fuzzy sets in 1965, in which he described the motivation of replicating human-like reasoning and detailed the mathematics of fuzzy set theory, and in 1973 he proposed his theory of fuzzy logic. Together, fuzzy sets and fuzzy logic provide the necessary foundations for a broad class of related innovations, including (but not limited to): fuzzy control (a practical approach to non-linear control using fuzzy if-then rules in fuzzy logic); fuzzy pattern recognition (a generalization of conventional pattern recognition techniques using fuzzy sets, such as fuzzy k-means generalizing k-means clustering); fuzzy database (generalizing classical database query language using fuzzy sets and fuzzy logic); fuzzy mathematics (generalizing conventional mathematics using fuzzy sets and fuzzy logic); and neuro-fuzzy systems (a synergistic combination of fuzzy logic and neural networks, providing the first interpretable AI system based on neural network learning). He was also on the Board of Governors for International Neural Network Society (INNS) in 2003.

In 1963, Zadeh became the chair of the Department of Electrical Engineering at the University of California, Berkeley. One of the lasting impacts of his leadership in this role was the expansion and integration of computer science. He initiated and completed in 1968 the transformation of the Electrical Engineering department at UC Berkeley to the Department of Electrical Engineering and Computer Science (EECS). This strategic move not only led UC Berkeley's advancement into the top ranks of computer science education and research, but also led other research universities globally to add computer science to their electrical engineering departments. In 1973, Zadeh received the prestigious Institute of Electronic and Electrical Engineers (IEEE) Education Award, largely in recognition of his performance as chair of EE and then EECS.

His other important services to UC Berkeley include his Academic Senate committee memberships: Academic Planning & Resource Allocation (1992–95); Committees (1969–70; 1980–81); Courses of Instruction (1975–80); and Faculty Awards (1990–92). Professor Zadeh graduated more than 50 PhD students, many of whom went on to become leaders in various areas of engineering, management and information sciences.^[96]

Zadeh photographed people around him.^[98] He was described as "quick to shrug off nationalism, insisting there are much deeper issues in life", noting in an interview: "The question really isn't whether I'm American, Russian, Iranian, Azerbaijani, or anything else. I've been shaped by all these people and cultures, and I feel quite comfortable among all of them." In the same interview, he also stated: "Obstinacy and tenacity, not being afraid to get embroiled in controversy – that's very much a Turkish tradition. That's part of my character, too. I can be very stubborn. That has probably been beneficial for the development of fuzzy logic." He described himself as "an American, mathematically oriented, electrical engineer of Iranian descent, born in Russia."

He and his wife, Fay Zadeh, had two children, Stella and Norman Zada. His wife authored the book My Life and Travels with the Father of Fuzzy Logic, recounting their shared travels to "exotic places" and their meetings with interesting people around the world.

A month prior to his death, the University of Tehran released an erroneous report stating that Zadeh had died, though it was withdrawn several days later.^[105] Zadeh died in his home in Berkeley, California, on 6 September 2017, at the age of 96. He was buried on 29 September 2017 at the First Alley of Honors in Baku, Azerbaijan, his birth city.^[26,97] His funeral was well attended by "highly respected people."

In his theory of fuzzy sets, Zadeh proposed using a membership function, with a range covering the interval [0,1], operating on the domain of all possible values. He proposed new operations for the calculus of logic and demonstrated that fuzzy logic was a generalisation of classical and Boolean logic. He also proposed fuzzy numbers as a special case of fuzzy sets, as well as the corresponding rules for consistent mathematical operations (fuzzy arithmetic).^[108,101]

Zadeh's research career has had a lasting impact on artificial intelligence (AI). Fuzzy sets and fuzzy logic are both motivated by our understanding of human cognition: that we are comfortable with concepts that have vague boundaries. This is well aligned with the Physical symbol system assumption in AI (by Allen Newell and Herbert A. Simon), inspired by another aspect of human cognition: that humans are comfortable with concepts that are described by symbols.

The concept of a linguistic variable in fuzzy logic connects a symbol that is typically a predicate in classical logic (e.g., "John is Bold", or in predicate logic – Bold(John)) – to linguistic values (e.g., "John is somewhat bold." or in fuzzy logic – Bold(John)=Somewhat) – which generalizes the binary value of predicate logic in two ways. First, the two possible values (True or False) in predicate logic are generalized to a continuum (typically from 0, which corresponds to False, to 1, which corresponds to True). This allows the expression of Bold(John)= 0.5, which indicates that John is midway between being devoid of boldness and being entirely bold. The second generalization enabled by fuzzy logic is to use a fuzzy set such as "somewhat bold" to describe a person's boldness level in a way that is more natural to human understanding and communication. Without this generalization, we can only describe the value of a person's boldness as a number (e.g., 0.5) or as an interval (e.g., [0.25, 0.75]). With this generalization, one can express the semantic meaning of "somewhat bold" as a fuzzy set in the domain of 0 and 1.

Zadeh was also an active contributor to the AI community, including at the Dartmouth Workshop that coined the term "artificial intelligence". He was subsequently a frequent contributor to leading AI conferences such as AAAI and IJCAI, as well as other top venues such as AI Magazine.

In 1952, Zadeh, alongside John R. Ragazzini, was credited with pioneering the development of the Z-transform method in discrete-time signal processing and analysis. These methods are now standard in digital signal processing, digital control, and other discrete-time systems used in industry and research.

Zadeh's work also included computing with words and perceptions, with his later papers including "From Search Engines to Question-Answering Systems" and "Toward a Generalized Theory of Uncertainty (GTU)—An Outline".^{[110,102,103]} Additionally, he served as an editor of the International Journal of Computational Cognition.

A complete list of publications is available.^[111,104] In 1965, L. A. Zadeh published in the Proceedings of the Symposium on System Theory (New York, N.Y., April 20, 21, 22, 1965) through the Polytechnic Institute of Brooklyn. His works have appeared in venues and outlets such as Information and Control, Journal of Cybernetics, IEEE Transactions on Systems, Man, and Cybernetics, and Springer. On December 4, 1974, North-Holland Publishing published his paper from Information Processing, Proceedings of the 6th IFIP Congress 1974, held in Stockholm, Sweden, from August 5 to 10, 1974. In 1975, Lotfi A. Zadeh, King-Sun Fu, Kokichi Tanaka, and Masamichi Shimura authored Fuzzy Sets and their Applications to Cognitive and Decision Processes, published by Academic Press.

Additional works include Q109950743, Q109951641, and Q109951958. In 2006, Lotfi A. Zadeh published From Computing with Numbers to Computing with Words in the Annals of the New York Academy of Sciences. On July 12, 2012, L.A. Zadeh's Computing with Words: Principal Concepts and Ideas was published by Springer-Verlag.

Zadeh was a Fellow of the Institute of Electrical and Electronics Engineers, the American Academy of Arts and Sciences, the Association for Computing Machinery, the Association for the Advancement of Artificial Intelligence, and the International Fuzzy Systems Association, as well as a member of the National Academy of Engineering.^[41] He was also a member of the Academies of Science of Azerbaijan, Bulgaria, Finland, Korea, and Poland, and of the International Academy of Systems Studies in Moscow. In addition to receiving 24 honorary doctorates—including an Honorary Doctor from Óbuda University in Budapest, Hungary in 2011—he was awarded an Honorary Professorship from the Azerbaijan State Oil Academy in 1993.^[43]

Among many other awards, Zadeh received the IEEE Education Medal in 1973 and the Eringen Medal in 1976. In 1992, he was awarded the IEEE Richard W. Hamming Medal for "seminal contributions to information science and systems, including the conceptualization of fuzzy sets." He subsequently received the American Society of Mechanical Engineers Rufus Oldenburger Medal in 1993, the IEEE Medal of Honor in 1995 for "pioneering development of fuzzy logic and its many diverse applications," and the American Automatic Control Council's Richard E. Bellman Control Heritage Award in 1998.

In 2001, Zadeh received the ACM Allen Newell Award, followed by the Outstanding Contribution Award from the Web Intelligence Consortium (WIC) in Halifax, Canada in 2003. In 2004, he was inducted into the Wall of Fame at the Heinz Nixdorf MuseumsForum (HNF) in Paderborn, Germany, and was awarded the V. Kaufmann Prize and Gold Medal by the International Association for Fuzzy-Set Management and Economy (SIGEF) in Barcelona, Spain on November 15, 2004. He received the J. Keith Brimacombe IPMM Award in 2005 in recognition of his development of fuzzy set theory and fuzzy logic, and the Benjamin Franklin Medal in Electrical Engineering from The Franklin Institute in Philadelphia in 2009 for inventing and developing the field of "fuzzy logic." Zadeh was inducted into the IEEE Intelligent Systems' AI's Hall of Fame in 2011 "for his work on soft computing, fuzzy logic, and neural-net theory." His later honors include the BBVA Foundation Frontiers of Knowledge Award in Information and Communication Technologies (ICT) in Spain in 2012, and the Golden Goose Award for Fuzzy Logic in 2017.

In 2014, the IEEE Systems, Man, and Cybernetics Society established the "Lotfi A. Zadeh Pioneer Award", which is given to honour a person or persons with "outstanding and pioneering contributions to academic and/or industrial research in systems science and engineering, human-machine systems, and/or cybernetics." The award is funded from a $100,000 donation from Zadeh's son, Norm Zadeh, and is administered by the IEEE. Nominees must have "pioneered and developed innovative research, executed in either academe or industry," that has resulted in major scientific advances in "systems science and engineering, human-machine systems, and/or cybernetics," with contributions made at least 15 years prior to the award date.^[116,2] In February 2019, ADA University in Baku, Azerbaijan presented the first "Lotfi Zadeh Scholarships", which honour the academic success of undergraduate students in the university's School of IT and Engineering. Winners of the scholarship receive a complete tuition waiver for the semester or semester-equivalent in which they achieved a 4.0 average.^[2]

On 4 February 2021, the IEEE Computational Intelligence Society and the International Fuzzy Systems Association (IFSA) jointly celebrated the centenary of Zadeh's birth.^[118,80] On 30 November 2021, Google honored Zadeh with a Google Doodle, marking the date in 1964 when his seminal paper Fuzzy sets was submitted for publication.^{[119,112,31,114]}

Further reading on Lotfi A. Zadeh includes "Lotfi Visions", a two-part interview with Jack J. Woehr published in Dr. Dobb's Journal in July 1994 (part 1) and August 1994 (part 2). Additional works include Enric Trillas's article "In Memory of L.A. Zadeh" in Mathware & soft computing (ISSN-e 1134–5632, Vol. 24, Nº. 2, 2017, págs. 16-18), as well as "Fuzzy Logic Is Not Fuzzy: World-renowned Computer Scientist Lotfi A. Zadeh" by I. Dzitac, F.G. Filip, and M.J. Manolescu, published in the International Journal of Computers Communications & Control (December 2017, Vol 12 No 6, pp. 748–789).

External resources on Lotfi A. Zadeh include his academic profile at the University of California, Berkeley's College of Engineering, Department of Electrical Engineering and Computer Science, materials by Didier Dubois and Henri Prade, and his role as Honorary Chair and Keynote Speaker at Agora University of Oradea. Additionally, Azerbaijan International has published multiple features on him, including the interview 'Reflections on the Beginnings of "Fuzzy Logic"' (Vol. 2:4, 1994, pp. 46–47) and a 'Short Biographical Sketch' (Vol. 2:4, Winter 1994, p. 49). The magazine also featured his Berkeley Commencement Speech, 'Commercialism and Human Values: When You Can't Stop for Lunch' (Vol. 6:1, Spring 1998, p. 65), and the retrospective piece 'Famous People: Then and Now, Lotfi Zadeh', reflecting on his childhood (Vol. 7:4, Winter 1999, pp. 28–29).