arbitrary

American  

[ahr-bi-trer-ee] / ˈɑr bɪˌtrɛr i /

adjective

1. subject to individual will or judgment without restriction; contingent solely upon one's discretion.

   an arbitrary decision.

2. decided by a judge or arbiter rather than by a law or statute.

3. having unlimited power; uncontrolled or unrestricted by law; despotic; tyrannical.

   an arbitrary government.

4. based on whim or personal preference, without reason or pattern; random.

   This is an unusual encyclopedia, arranged by topics in a more or less arbitrary order.

5. Mathematics. undetermined; not assigned a specific value.

   an arbitrary constant.

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noun

plural

arbitraries

1. Printing. arbitraries, (in Britain) peculiar.

arbitrary British  

/ ˈɑːbɪtrərɪ /

adjective

1. founded on or subject to personal whims, prejudices, etc; capricious

2. having only relative application or relevance; not absolute

3. (of a government, ruler, etc) despotic or dictatorial

4. maths not representing any specific value

   an arbitrary constant

5. law (esp of a penalty or punishment) not laid down by statute; within the court's discretion

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Other Word Forms

• arbitrarily adverb
• arbitrariness noun
• nonarbitrary adjective
• unarbitrary adjective

Etymology

Origin of arbitrary

First recorded in 1400–50; late Middle English, from Latin arbitrārius “uncertain” (i.e., depending on an arbiter's decision); arbiter, -ary

Explanation

Something that's arbitrary seems like it's chosen at random instead of following a consistent rule. Team members would dislike their coach using a totally arbitrary method to pick starting players. Even though arbitrary comes from a word meaning "judge" (arbiter), that doesn't mean judges are always fair. Calling a decision-maker arbitrary is usually a negative thing, suggesting the person is making rules based on whim rather than justice. A coach who selects starting players arbitrarily isn't strictly applying a rule; he could just be picking names out of a hat.

Example Sentences

That’s a quintessential example of an agency action that’s unlawfully arbitrary and capricious.

From Slate • Mar. 27, 2026

In her ruling, she said the government's designation of Anthropic as a supply chain risk was "likely both contrary to law and arbitrary and capricious."

From Barron's • Mar. 26, 2026

“Bad years for the S&P 500 are due to very specific factors, not just bad luck or arbitrary changes in investor sentiment,” said Nicholas Colas, co-founder of DataTrek, in commentary shared with MarketWatch on Tuesday.

From MarketWatch • Mar. 24, 2026

In it he argued that the large economic models then dominant rested on assumptions so arbitrary they were, in his word, “incredible.”

From The Wall Street Journal • Mar. 17, 2026

Then they decided to go after him by imposing additional and arbitrary restrictions.

From "Born a Crime: Stories from a South African Childhood" by Trevor Noah

Related Words

• capricious
• discretionary
• erratic
• frivolous
• inconsistent
• irrational
• irresponsible
• random
• subjective
• unreasonable
• willful