adj
arbitrary
AH-bih-truh-ree
adj
1
Based on personal choice or chance rather than any clear reason, rule, or system.
"The rule felt completely arbitrary — nobody could explain why it existed."
"They picked a seemingly arbitrary cutoff date for applications."
2
Used, in mathematics and logic, to mean "any one you like" out of all the possibilities — not random in the everyday sense, but unspecified.
"Let n be an arbitrary positive integer."
How to Use Arbitrary
Learner’s notesIn plain EnglishDecided without a clear reason, or (in maths) simply "any given one".
Common mistake
In everyday use "arbitrary" often carries a negative sense of "unfair" or "unjustified"; in maths and logic it's neutral, just meaning "unspecified".
Common pairings
arbitrary decision
arbitrary rule
seemingly arbitrary
Word Forms
more arbitrary comparative, arbitraries plural, most arbitrary superlative
Study it as flashcards or scroll it in Flow — saved to your collection.
Test yourself on “arbitrary”
A quick quiz — meaning, synonyms & usage
→
Fill the Gap
Can you complete this real example?
The rule felt completely _____ — nobody could explain why it existed.
Etymology
From Latin arbitrarius, "uncertain, subject to a judge's discretion", from arbiter, "judge".