[koo d; unstressed kuh d]


a simple past tense of can1.

auxiliary verb

(used to express possibility): I wonder who that could be at the door. That couldn't be true.
(used to express conditional possibility or ability): You could do it if you tried.
(used in making polite requests): Could you open the door for me, please?
(used in asking for permission): Could I borrow your pen?
(used in offering suggestions or advice): You could write and ask for more information. You could at least have called me.

Origin of could

Middle English coude, Old English cūthe; modern -l- (from would1, should) first attested 1520–30
Can be confusedcould should would (see usage note at should)

Usage note

See care.


[kan; unstressed kuh n]

auxiliary verb, present singular 1st person can, 2nd can or (Archaic) canst, 3rd can, present plural can; past singular 1st person could, 2nd could or (Archaic) couldst, 3rd could, past plural could.

to be able to; have the ability, power, or skill to: She can solve the problem easily, I'm sure.
to know how to: He can play chess, although he's not particularly good at it.
to have the power or means to: A dictator can impose his will on the people.
to have the right or qualifications to: He can change whatever he wishes in the script.
may; have permission to: Can I speak to you for a moment?
to have the possibility: A coin can land on either side.

verb (used with or without object), present singular 1st person can, 2nd can or (Archaic) canst, 3rd can, present plural can; past singular 1st person could, 2nd could or (Archaic) couldst, 3rd could, past plural could; imperative can; infinitive can; past participle could; present participle cun·ning.

Obsolete. to know.

Origin of can

before 900; Middle English, Old English, present indicative singular 1st, 3rd person of cunnan to know, know how; cognate with German, Old Norse, Gothic kann; see ken, know1
Can be confusedcan may shall will (see usage note at the current entry) (see usage note at shall)

Usage note

Can1 and may1 are frequently but not always interchangeable in senses indicating possibility: A power failure can (or may ) occur at any time. Despite the insistence by some, that can means only “to be able” and may means “to be permitted,” both are regularly used in seeking or granting permission: Can (or May ) I borrow your tape recorder? You can (or may ) use it tomorrow. Sentences using can occur chiefly in spoken English. May in this sense occurs more frequently in formal contexts: May I address the court, Your Honor? In negative constructions, can't or cannot is more common than may not : You can't have it today. I need it myself. The contraction mayn't is rare.
Can but and cannot but are formal and now somewhat old-fashioned expressions suggesting that there is no possible alternative to doing something. Can but is equivalent to can only : We can but do our best. Cannot but is the equivalent of cannot help but : We cannot but protest against these injustices. See also cannot, help.




a sealed container for food, beverages, etc., as of aluminum, sheet iron coated with tin, or other metal: a can of soup.
a receptacle for garbage, ashes, etc.: a trash can.
a bucket, pail, or other container for holding or carrying liquids: water can.
a drinking cup; tankard.
a metal or plastic container for holding film on cores or reels.
Slang: Usually Vulgar. toilet; bathroom.
Slang. jail: He's been in the can for a week.
Slang: Sometimes Vulgar. buttocks.
cans, Slang. a set of headphones designed to cover the ears. Compare earbuds.
Military Slang.
  1. a depth charge.
  2. a destroyer.

verb (used with object), canned, can·ning.

to preserve by sealing in a can, jar, etc.
Slang. to dismiss; fire.
Slang. to throw (something) away.
Slang. to put a stop to: Can that noise!
to record, as on film or tape.

Origin of can

before 1000; Middle English, Old English canne, cognate with German Kanne, Old Norse kanna, all perhaps < West Germanic; compare Late Latin canna small vessel Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for could


verb (takes an infinitive without to or an implied infinitive)

used as an auxiliary to make the past tense of can 1
used as an auxiliary, esp in polite requests or in conditional sentences, to make the subjunctive mood of can 1 could I see you tonight?; she'd telephone if she could
used as an auxiliary to indicate suggestion of a course of actionyou could take the car tomorrow if it's raining
(often foll by well) used as an auxiliary to indicate a possibilityhe could well be a spy

Word Origin for could

Old English cūthe; influenced by would, should; see can 1



verb past could (takes an infinitive without to or an implied infinitive) (intr)

used as an auxiliary to indicate ability, skill, or fitness to perform a taskI can run a mile in under four minutes
used as an auxiliary to indicate permission or the right to somethingcan I have a drink?
used as an auxiliary to indicate knowledge of how to do somethinghe can speak three languages fluently
used as an auxiliary to indicate the possibility, opportunity, or likelihoodmy trainer says I can win the race if I really work hard

Word Origin for can

Old English cunnan; related to Old Norse kunna, Old High German kunnan, Latin cognōscere to know, Sanskrit jānāti he knows; see ken, uncouth


See may 1




a container, esp for liquids, usually of thin sheet metala petrol can; beer can
another name (esp US) for tin (def. 2)
Also called: canful the contents of a can or the amount a can will hold
a slang word for prison
US and Canadian a slang word for toilet or buttocksSee toilet
US navy a slang word for destroyer
navy slang a depth charge
a shallow cylindrical metal container of varying size used for storing and handling film
can of worms informal a complicated problem
carry the can See carry (def. 37)
in the can
  1. (of a film, piece of music, etc) having been recorded, processed, edited, etc
  2. informalarranged or agreedthe contract is almost in the can

verb cans, canning or canned

to put (food, etc) into a can or cans; preserve in a can
(tr) US slang to dismiss from a job
(tr) US informal to stop (doing something annoying or making an annoying noise) (esp in the phrase can it!)
(tr) informal to reject or discard

Word Origin for can

Old English canne; related to Old Norse, Old High German kanna, Irish gann, Swedish kana sled
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 could

Old English cuðe, past tense of cunnan "to be able" (see can (v.1)); ending changed 14c. to standard English -d(e). The excrescent -l- was added 15c.-16c. on model of would, should, where it is historical.



"to put up in cans," 1860, from can (n.1). Sense of "to fire an employee" is from 1905. Related: Canned; canning.



Old English 1st & 3rd person singular present indicative of cunnan "know, have power to, be able," (also "to have carnal knowledge"), from Proto-Germanic *kunnan "to be mentally able, to have learned" (cf. Old Norse kenna "to know, make known," Old Frisian kanna "to recognize, admit," German kennen "to know," Gothic kannjan "to make known"), from PIE root *gno- (see know).

Absorbing the third sense of "to know," that of "to know how to do something" (in addition to "to know as a fact" and "to be acquainted with" something or someone). An Old English preterite-present verb, its original past participle, couth, survived only in its negation (see uncouth), but cf. could. The present participle has spun off as cunning.



Old English canne "a cup, container," from Proto-Germanic *kanna (cf. Old Saxon, Old Norse, Swedish kanna, Middle Dutch kanne, Dutch kan, Old High German channa, German Kanne). Probably an early borrowing from Late Latin canna "container, vessel," from Latin canna "reed," also "reed pipe, small boat;" but the sense evolution is difficult.

Modern "air-tight vessel of tinned iron" is from 1867 (can-opener is from 1877). Slang meaning "toilet" is c.1900, said to be a shortening of piss-can. Meaning "buttocks" is from c.1910.

Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with could


see can (could) do with; see with half an eye, could. Also see under can; couldn't.


In addition to the idioms beginning with can

  • can do with
  • canned laughter
  • can of worms

also see:

  • as best one can
  • before you can say Jack Robinson
  • bite off more than one can chew
  • carry the can
  • catch as catch can
  • game that two can play
  • get the ax (can)
  • in the can
  • more than one can shake a stick at
  • no can do
  • you can bet your ass
  • you can lead a horse to water
  • you can say that again
  • you never can tell

Also see undercan't.

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