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Used to indicate that either or both of the items connected by it are involved.
Usage Note: And/or is widely used in legal and business writing. Its use in general writing to mean "one or the other or both" is acceptable but often sounds stilted. See Usage Note at or1.
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.
(coordinating) used to join terms when either one or the other or both is indicated: passports and/or other means of identification.
Usage: Many people think that and/or is only acceptable in legal and commercial contexts. In other contexts, it is better to use or both: some alcoholics lose their jobs or their driving licences or both (not their jobs and/or their driving licences)
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
(used to imply that either or both of the things mentioned may be affected or involved): accident and/or health insurance.
usage: and/or is used primarily in business and legal writing. Some object to its use in general writing, where it occasionally occurs: She spends her time entertaining and/or traveling. In such writing either and or or is usu. adequate. If a greater distinction is needed, another phrasing is available: entertaining or traveling, or both.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.