ad-(word root) to, towardExamples of words with the root ad-: advent, adverseAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreead-pref.1. or ac- or af- or ag- or al- or ap- or as- or at- Toward; to. Before c, f, g, k, l, p, q, s, and t, ad- is usually assimilated to ac-, af-, ag-, ac-, al-, ap-, ac-, as-, and at-, respectively.2. Near; at: adrenal.[Latin, from ad, to; see ad- 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.ad- prefix 1. to; towards: adsorb; adverb. 2. near; next to: adrenal. [from Latin: to, towards. As a prefix in words of Latin origin, ad- became ac-, af-, ag-, al-, an-, acq-, ar-, as-, and at- before c, f, g, l, n, q, r, s, and t, and became a- before gn, sc, sp, st]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ad1 (æd) n. 1. an advertisement. 2. advertising: an ad agency. [1835?45; by shortening] ad2 (æd) n. Tennis. advantage (def. 4). [1925?30; by shortening] ad- a prefix occurring in verbs or verbal derivatives borrowed from Latin, where it meant ?toward? and indicated direction, tendency, or addition: adjoin. For variants before a following consonant, see a-5, ac-, af-, ag-, al-, an-2, ap-1, ar-, as-, at-. [