-logy or -ologysuff.1. Discourse; expression: phraseology.2. Science; theory; study: dermatology; sexology.[Middle English -logie, from Old French, from Latin -logia, from Greek -logi? (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, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.-logy n combining form 1. indicating the science or study of: musicology. 2. indicating writing, discourse, or body of writings: trilogy; phraseology; martyrology. [from Latin -logia, from Greek, from logos word; see logos] -logical, -logic adj combining form -logist n combining formCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014lo?gy (?lo? gi) adj. -gi?er, -gi?est. lacking physical or mental energy or vitality; sluggish; dull; lethargic. [1840?50, Amer.; perhaps