Abbreviations - Notes-bibliography style: the basic form - Part II. Source Citation

A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Abbreviations
Notes-bibliography style: the basic form
Part II. Source Citation

In notes, abbreviate terms such as editor, translator, and volume (ed., trans., and vol.). In bibliography entries, these terms are often spelled out when they introduce an element (Edited by) but abbreviated when they conclude it (ed.). The plural is usually formed by adding s (eds.) unless the abbreviation ends in an s (use trans. for both singular and plural).