Some academic books overcome such obstacles that they should be accompanied by trumpets and parades when they come out. Two volumes published by Walter de Gruyter in 2005 and 2009 completed an edition of Hesychius’ lexicon which was begun in 1914 and carried on through two world wars, shortages of money, economic crises, the closing of the original publisher, the death of the original editor, and the illness of his replacement. This edition, in turn, was the descendant of one published in Venice as early as 1514. The editor, M. Musevius, wrote his corrections on top of the original text before lending the manuscript to the printer, and that turned out to be unfortunate because his manuscript was the last one in existence. The manuscript, in turn, had been made circa 1430 and was linked to Hesychius’ own work in the fifth or sixth century by a long process of copying, condensing, and interpolating. The purpose of a scholarly edition is to publish a text which is as close to what Hesychius actually wrote as possible, with a few comments on sources, especially controversial entries, and related texts.
Hesychius was a Greek lexicographer, which is to say that he studied rare or dialectical Greek words and commented on their meaning, origin, and usage. In doing so he or his sources used and sometimes quoted many books which have now been lost. His work is important for Achaemenid studies because it contains several dozen Iranian words, some of them known nowhere else in the tattered fragments of ancient literature which survive. (An overview is available here).
A typical entry is as follows:
κάρδακες΄ οἱ στρατευσάμενοι βάρβαροι ὑπὸ Περσῶν. καὶ ἐν Άσίᾳ οὕτω καλοῦσι τοὺς στρατιώτας, οὐκ ἀπὸ ἕθνους ἥ τόπου
“Kardakes: The campaigning barbarians under the Persians. And in Asia they call the soldiers this, not by nation or place.” (my translation; I have spared the reader a view of accented Greek in WordPress’ default font)
Marginal notes mention Hesychius’ source (another lexicographer called Diogenianus) and that the editor has corrected the manuscript’s spelling of two words.
Ancient lexicographies were very helpful for understanding ancient Greek, and sometimes preserve words or meanings attested nowhere else. Unfortunately, lexicographical works which survive have usually been trimmed of their quotations and citations, and they are not free from errors or guesses. Scholars still debate who the kardakes were.
Edit 2015/02/02: Added two missing words.