Noun

(uncountable) The quality of being different.

(countable) A characteristic of something that makes it different from something else.

* {{quote-magazine, title=Towards the end of poverty

, date=2013-06-01, volume=407, issue=8838, page=11, magazine=(The Economist) citation , passage=But poverty’s scourge is fiercest below $1.25 (the average of the 15 poorest countries’ own poverty lines, measured in 2005 dollars and adjusted for differences in purchasing power): people below that level live lives that are poor, nasty, brutish and short.}}

(countable) A disagreement or argument.

We have our little differences , but we are firm friends.

* Shakespeare

What was the difference ? It was a contention in public.

* T. Ellwood

Away therefore went I with the constable, leaving the old warden and the young constable to compose their difference as they could.

(countable, uncountable) Significant change in or effect on a situation or state.

* 1908 , (Kenneth Grahame), (The Wind in the Willows)

The line of the horizon was clear and hard against the sky, and in one particular quarter it showed black against a silvery climbing phosphorescence that grew and grew. At last, over the rim of the waiting earth the moon lifted with slow majesty till it swung clear of the horizon and rode off, free of moorings; and once more they began to see surfaces—meadows wide-spread, and quiet gardens, and the river itself from bank to bank, all softly disclosed, all washed clean of mystery and terror, all radiant again as by day, but with a difference that was tremendous.

(countable) The result of a subtraction; sometimes the absolute value of this result.

(obsolete) Choice; preference.

* Spenser

That now be chooseth with vile difference / To be a beast, and lack intelligence.

(heraldry) An addition to a coat of arms to distinguish two people's bearings which would otherwise be the same. See augmentation and cadency.

(logic) The quality or attribute which is added to those of the genus to constitute a species; a differentia.

(logic circuits) A Boolean operation which is TRUE when the two input variables are different but is otherwise FALSE; the XOR operation ($\backslash scriptstyle\; A\; \backslash overline\; B\; +\; \backslash overline\; A\; B$).

(relational algebra) the set of elements that are in one set but not another ($\backslash scriptstyle\; A\; \backslash overline\; B$).

Noun

(en noun)

A confrontation; a dare.

# An instigation or antagonization intended to convince a person to perform an action they otherwise would not.

#*{{quote-magazine, date=2013-11-30, volume=409, issue=8864, magazine=(The Economist), author=Paul Davis

, title= Letters: Say it as simply as possible , passage=Congratulations on managing to use the phrase “preponderant criterion” in a chart (“ On your marks”, November 9th). Was this the work of a kakorrhaphiophobic journalist set a challenge by his colleagues, or simply an example of glossolalia?}}

# A bid to overcome something.

#* {{quote-news, year=2012, date=May 5, author=Phil McNulty, work=BBC Sport

, title= Chelsea 2-1 Liverpool , passage=For Liverpool, their season will now be regarded as a relative disappointment after failure to add the FA Cup to the Carling Cup and not mounting a challenge to reach the Champions League places.}}

# (sports) An attempt to take possession; a tackle

#* {{quote-news, year=2011, date=October 1, author=Saj Chowdhury, work=BBC Sport

, title= Wolverhampton 1-2 Newcastle , passage=Argentine midfielder Jonas Gutierrez added a superb second when he surged past four challenges to fire in low.}}

# A summons to fight a duel; also, the letter or message conveying the summons.

# The act of a sentry in halting a person and demanding the countersign, or (by extension) the action of a computer system demanding a password, etc.

A difficult task, especially one that the person making the attempt finds more enjoyable because of that difficulty.

(label) A procedure or action.

# (legal, rare) A judge's interest in the result of the case for which he or she should not be allowed to sit the case, e.g. a conflict of interest.

# The act of appealing a ruling or decision of a court of administrative agency.

# The act of seeking to remove a judge, arbitrator or other judicial or semi-judicial figure for reasons of alleged bias or incapacity.

# (label) An exception to a person as not legally qualified to vote. The challenge must be made when the ballot is offered.

(label) The opening and crying of hounds at first finding the scent of their game.