from The American Heritage® Dictionary of the English Language, 4th Edition
- suffix Discourse; expression: phraseology.
- suffix Science; theory; study: dermatology; sexology.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- suffix A branch of learning; a study of a particular subject.
- suffix Something said, or a way of speaking, a narrative.
from the GNU version of the Collaborative International Dictionary of English
- suffix A combining form denoting a discourse, treatise, doctrine, theory, science.
Middle English -logie, from Old French, from Latin -logia, from Greek -logiā (from logos, word, speech; see leg- in Indo-European roots) and from -logos, one who deals with (from legein, to speak; see leg- in Indo-European roots).(American Heritage® Dictionary of the English Language, Fourth Edition)
The English -logy suffix originates with loanwords from the Greek, usually via Latin and French, where the suffix is an integral part of the word loaned. E.g. astrology from astrologia, since the 16th century. (Wiktionary)