arbitrary
UK /ˈɑː.bɪ.trə.ri/ US /ˈɑːr.bə.trer.i/ Syllables: ar-bi-trar-y
Quick answer
Decided by chance or personal preference rather than by reason, rule, or system.
Arbitrary describes a choice or a decision made by chance or by personal wish, without a clear reason or rule behind it. If a teacher gives marks at random, the marks are arbitrary. The word is often negative when it is about power: an arbitrary rule feels unfair because it does not follow any fair system. In mathematics, it simply means any value you like.
"The judge felt the fine was arbitrary and not based on any clear standard."Meanings
- Based on chance or personal wish, not on a reason or a rule.
- Using power without limits or fair rules.
Example sentences
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"The deadline seemed arbitrary to everyone."
Level C1, Meaning 1
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"Choose any arbitrary number between one and ten."
Level C1, Meaning 1
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"Arbitrary arrests were common under the old government."
Level C1, Meaning 2
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"The price is not arbitrary: it is based on cost."
Level C1, Meaning 1
Synonyms and antonyms
Synonyms
Antonyms
Look-alikes and common mistakes
- random : Random means by chance with no pattern. Arbitrary means chosen without a reason, but a person may have chosen it.
Word family and forms
Word partners
Words and phrases that often go with "arbitrary".
- an arbitrary decision
- arbitrary rule
- completely arbitrary
- arbitrary choice
- seem arbitrary
- arbitrary number
Origin
Arbitrary comes from Latin arbitrarius, which meant depending on the decision of an arbiter. An arbiter was a judge or a witness, and the word later came to mean a decision that rests on will alone.
Checked against: Wiktionary, the free dictionary, Dictionary.com.
How to remember it
Arbitrary and arbiter share "arbit": an arbitrary decision is whatever the arbiter happens to choose.
Test yourself
Which word fits the gap? "The deadline seemed _____ to everyone."
Answer: arbitrary
In your own words, what does "arbitrary" mean?
Decided by chance or personal preference rather than by reason, rule, or system.
Learn next at C1
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Sources and credits
- Wiktionary, the free dictionary (CC BY-SA 4.0) · used for the origin, pronunciation · checked Oct 19, 2026
- Dictionary.com · used for the origin · checked Oct 19, 2026
Last reviewed October 19, 2026. Report a mistake on this page