-ology(word root) a science or branch of knowledgeExamples of words with the root -ology: biology, geology, psychologyAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreeol·o·gy (?l??-j?)n. pl. ol·o·gies Informal A branch of learning.[From -ology.]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.ology (??l?d??) n, pl -giesinformal a science or other branch of knowledge[C19: abstracted from words with this ending, such as theology, biology, etc; see -logy]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014