For English readers with a knowledge of Latin and Greek wanting to consult more scholarly editions than the Loeb series, the Oxford Classical Texts (Scriptorum Classicorum Bibliotheca Oxoniensis) are renowned for their reliability and presentation. The series consists of texts without commentaries but with brief apparatus criticus at the foot of each page. There are now over 100 volumes, representing the greater part of classical Greek and Latin literature. The aim of the series is to include the works of all the principal classical authors. Although this has been largely accomplished, new volumes are still being published to fill the remaining gaps and old editions are being revised in the light of recent research or replaced.
For a full list see: Oxford Classical Texts – Oxford University Press
Peters, F. E. (1967). Greek Philosophical Terms: A Historical Lexicon. New York: New Your University Press.
This book defines and translates key terms used by pre-Christian philosophers up to the time of Proclus, with special references to the writings of the philosophers as they developed nuances and new meanings for the terms. Entries are arranged in dictionary style, but a knowledge of Greek is not necessary to use the book, since an English-Greek index provides the reader with Greek equivalents of English terms, with cross-reference to the main text.
Urmson, J. O. (1990). The Greek Philosophical Vocabulary. London: Duckworth.
All entries give primary sources and Greek in transliterated form and English translation