Logeion provides simultaneous lookup in the reference sources contained in the Perseus Project. It covers both Greek and Latin, and draws from multiple dictionaries. It provides results from each dictionary, as well as information about the frequency of the word and examples of its use in ancient sources. It also includes reference works on ancient people, places, and mythology.

An online searchable version of Liddell-Scott-Jones (LSJ), the premier lexicon for classical Greek. LSJ was first published in 1843 by Oxford Clarendon Press edited by Henry George Liddell and Robert Scott and based on earlier lexicographical work by Schneider and Passow.