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definitions

cannot

[kan-ot, ka-not, kuh-]
verb
  1. a form of ·can not.
Idioms
  1. cannot but, have no alternative but to: We cannot but choose otherwise.

Origin of cannot

Middle English word dating back to 1350–1400

Usage note

Cannot is sometimes also spelled can not. The one-word spelling is by far the more common: Interest rates simply cannot continue at their present level. The contraction can't is most common in speech and informal writing. See also can1.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for cannot

cannot

verb
  1. an auxiliary verb expressing incapacity, inability, withholding permission, etc; can not
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for cannot
v.

c.1400, from can (v.1) + not. Old English expressed the notion by ne cunnan.

Online Etymology Dictionary, © 2010 Douglas Harper
Idioms and Phrases with cannot

cannot

see under can't.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.