Greek texts today are simply printed with the letters of the Greek alphabet, of which the most arcane difficulty is the two forms of the lower-case sigma. But Greek texts from the Renaissance into the early nineteenth century could be printed with a baffling array of ligatures and abbreviations, mimicking the manuscripts on which they were based. These two tables will help in deciphering earlier printed Greek books.
A list of ligatures and abbreviations used to embellish writings in Greek, from Alphabetum Graecum, printed in 1550 by Guil. Morelium (Guillaume Morel).
An engraved table of Abbreviations and Connexions from The Elements of Greek Grammar, printed in 1816