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arbitrary

/ˈɑːrbətreri//ˈɑːbɪtrəri/·adjective
based on whim or chance rather than reason or system
Fig. 1 — I watch coloured tiles drop one by one into a neat grid, and every tile lands square — dead centre, edges true, not one of them crooked.
01Definition

An arbitrary choice is one that reasons cannot explain — from the Latin arbiter, 'judge': what is arbitrary is decided by someone's discretion rather than by any rule the rest of us could check. A border drawn as a straight line through living communities is arbitrary; rules that change weekly are arbitrary; the choice between identical options is arbitrary by necessity. The word carries a quiet accusation: where the arbitrary begins, justification has ended.

02In use
  • iThe colonial border was an arbitrary line that ignored the people living along it.
  • iiEmployees complained that the new rules felt arbitrary, changing from week to week.
  • iiiWhen two candidates' merits coincide exactly, any choice between them is arbitrary.
03Collocations
  • an arbitrary decision
  • seemingly arbitrary
  • arbitrary rules
  • an arbitrary line
  • arbitrary arrest

Family arbitrarily (adverb) · arbitrariness (noun)

04Relations

=random, capricious, whimsical, unjustified, discretionary, haphazard

≠reasoned, principled, coherent, pragmatic

05Compared
PairThe difference
arbitrary vs haphazarda choice made with no logic → arbitrary; no chooser at all, just chance → haphazard.
06TOEFL & IELTS

A TOEFL linguistics classic: passages on language note that 'the relationship between a word and its meaning is arbitrary' — recognize the claim, it gets tested. Science texts speak of arbitrary units and constants; politics passages of arbitrary arrest and arbitrary power. Pronunciation trap: US keeps four syllables with stress up front (/ˈɑːrbətreri/), UK compresses (/ˈɑːbɪtrəri/).

07Asked
Where does arbitrary come from?
From Latin arbiter, 'judge' — what is arbitrary was originally whatever lay within a judge's discretion. The family is still working: an arbiter settles disputes, arbitration is judgment by a private referee. The drift tells its own story: from a judge's rightful discretion to discretion with no rules behind it at all.
What does 'arbitrary and capricious' mean in law?
It is the standard American courts use to strike down agency decisions: a ruling made without reasoned explanation — ignoring the evidence, or unconnected to it — is 'arbitrary and capricious' and can be overturned. The doubled phrase is legal boilerplate, but the test inside it is the word's plain meaning: a decision no reasons can support.
What does arbitrary mean in maths?
Something neutral, for once: 'let x be an arbitrary integer' means any integer whatsoever — the proof must survive every choice. Arbitrary constants and arbitrary units work the same way: the value was picked freely because the argument does not depend on it. Mathematics keeps the 'no reason for this one' core and strips away the blame.
Is arbitrary a negative word?
In everyday and political English, usually yes — calling a rule or a decision arbitrary accuses it of lacking justification. In technical writing it is neutral (arbitrary values, arbitrary precision). The register rule: applied to power over people, it condemns; applied to symbols and numbers, it merely means 'freely chosen'.
What is the difference between arbitrary and random?
Random means chance chose — no one decided ('a random sample'). Arbitrary means someone decided, but without reasons anyone could check. The tiles in the scene above land in a flawless grid, so nothing is random — yet the colours follow pure whim, which is exactly where the arbitrariness lives: in the reasons, not the hand.
What does 'arbitrary arrest' mean?
Detention without lawful grounds or fair process — arrest at an official's whim rather than by rule. The phrase is anchored in Article 9 of the Universal Declaration of Human Rights ('no one shall be subjected to arbitrary arrest, detention or exile'), which is why human-rights reporting reaches for this word so often.
What is the difference between arbitrary and haphazard?
The compressed version: arbitrary is unjustified in the choosing but can be perfectly tidy in the doing; haphazard is untidy in the doing itself. The full contrast, with both animated scenes, is on the arbitrary vs haphazard page in the 'Compared' list above.