IN 1621, an Italian explorer found an unknown form of writing in the ruins of the ancient Persian city of Persepolis. During the 1800’s, archaeologists excavating in Iraq unearthed numerous similar inscriptions on clay tablets and palace walls. The texts preserve the Mesopotamian languages spoken by such rulers as Sargon II, Hammurabi, and Nebuchadnezzar II. The script, consisting of wedge-shaped strokes, came to be known as cuneiform.

This type of writing held the key to understanding the great civilizations of ancient Mesopotamia. Scholars working to decipher these documents thus saw the need for a comprehensive dictionary of Akkadian, of which language Assyrian and Babylonian are closely-related dialects.

This challenging project was undertaken by the Oriental Institute of the University of Chicago, U.S.A., in 1921, and it was completed 90 years later, in 2011. The result is the monumental 26-part Assyrian Dictionary, which contains more than 9,700 pages. It covers  languages and dialects used in Iran, Iraq, Syria, and Turkey, from the third millennium B.C.E. to 100 C.E.

Why is the dictionary so extensive? Why did it take so long to compile? And who would be interested in using it?

“The dictionary is not simply a word list,” explains Gil Stein, director of Chicago’s Oriental Institute. Rather, “by detailing the history and range of uses of each word, this unique volume is in essence a cultural encyclopedia of Mesopotamian history, society, literature, law, and religion. It is an indispensable research tool for any scholar anywhere who seeks to explore the written record of Mesopotamian civilization.”

The editors realized early in their work that “in order to do justice to the meaning of a word, all its occurrences must be collected, and that they must be collected not simply as words, but as words with as much accompanying text as would be needed to determine the meaning of the word within one particular context or usage.” The dictionary thus became a compendium of quotations from and translations of original cuneiform passages in which the defined words appear.

Literally millions of cuneiform texts have come to light over the last two centuries, and they deal with a huge range of subject matter. Assyro-Babylonian, or Akkadian, was the international language of diplomacy throughout the ancient Middle East. Yet, people in the same area produced literature; engaged in trade; studied mathematics, astronomy, and magic; established laws; developed professions; and practiced religion. Hence, their writings on all these and other topics furnish a wealth of information.

The picture these texts paint is not one of an alien civilization. “A lot of what you see is absolutely recognisable​—people expressing fear and anger, expressing love, asking for love,” says Matthew Stolper, a University of Chicago professor of Assyriology who worked on the project at intervals for 30 years. “There are inscriptions from kings that tell you how great they are,” he adds, “and inscriptions from others who tell you those guys weren’t so great.” And texts from Nuzi, in modern-day Iraq, document 3,500-year-old legal disputes over such questions as a widow’s inheritance, an irrigated field, and a borrowed donkey.

Assyriologists from all over the world contributed to the project. The institute’s staff spent decades filing close to 2,000,000 index cards illustrating word usage. The first volume went to press in 1956. Since then, 25 more installments have appeared as they became ready. The whole set sells for about $2,000 (U.S.), but all the information has been made available online, free of charge.

A full 90 years were needed to complete the dictionary. Even so, those who worked on this mammoth project recognize its limitations. Says one article on the subject: “They still do not know what some words mean, and because new discoveries are being made all the time, it is . . . a work in progress.”