Arbitrary means based on personal choice, chance, or preference rather than a clear reason, rule, or logical system. It can also describe a decision, rule, or use of power that seems unfair because it is made without a reasonable or consistent basis.
For example, if a manager chooses one employee for a promotion simply because they personally like that person, without considering qualifications or performance, the decision may be described as arbitrary.
The word can have slightly different meanings depending on context. In everyday English, it often suggests something random or unsupported by a clear reason. In formal contexts, it can suggest an exercise of power without sufficient regard for rules, rights, or fairness.
What Does “Arbitrary” Mean?
Arbitrary is an adjective used to describe something that is:
- Based on personal preference rather than objective reasoning
- Chosen without a clear or stated reason
- Determined by chance
- Not guided by a consistent rule or system
- Sometimes unfair, unreasonable, or unpredictable
Simple definition
Arbitrary = chosen or decided without a clear, logical, or consistent reason.
For example:
“The deadline seems arbitrary.”
This means the deadline appears to have been selected without an obvious reason or principle.
Oxford similarly defines arbitrary as something that does not seem to be based on a reason, system, or plan and that may sometimes appear unfair.
Arbitrary Meaning in Simple English
In simple terms, arbitrary means “decided without a good or obvious reason.”
Imagine a teacher says:
“I picked 17 as the maximum number of students because I felt like it.”
If there is no practical, educational, or safety-related reason for choosing 17, that number could be described as arbitrary.
Another example:
“The company introduced an arbitrary rule that employees could only use blue pens.”
If there is no clear reason for the rule, employees might consider it arbitrary.
However, arbitrary does not always mean completely random. Sometimes a person has a reason for making a choice, but the reason is personal, unexplained, or not based on an established standard.
Examples of Arbitrary
Here are some easy examples to understand the word:
- The manager made an arbitrary decision to change the schedule.
- The decision did not appear to have a clear reason.
- The number 10 was an arbitrary choice.
- Someone selected 10 without a particular objective reason.
- The rules seemed arbitrary and inconsistent.
- The rules did not appear to follow a clear or consistent system.
- She chose an arbitrary color for the background.
- She selected a color without a specific reason.
- The judge cannot make arbitrary decisions.
- Decisions should be based on law and relevant facts rather than personal preference.
- The deadline felt arbitrary.
- There was no obvious explanation for why that particular deadline was chosen.
- The researchers selected an arbitrary starting point.
- The starting point was selected for convenience rather than because it had an inherently special significance.
What Is an Arbitrary Decision?
An arbitrary decision is a decision made without a clear, rational, consistent, or established basis.
For example:
A company has 20 qualified applicants but chooses one person without considering experience, education, skills, or interview performance.
If the selection is based only on the decision-maker’s unexplained preference, it could be called arbitrary.
Arbitrary decision example
Suppose a supervisor says:
“I’m allowing employees to work from home on Fridays, but only employees whose names start with A through M.”
If there is no business reason for this distinction, employees might reasonably describe the rule as arbitrary.
What Does Arbitrary Mean in Law?
In legal contexts, arbitrary generally has a more serious meaning.
An action may be described as arbitrary when an authority makes a decision without adequately following applicable law, established standards, relevant evidence, or a rational basis.
For example:
“The agency’s decision was challenged as arbitrary.”
This suggests that someone is arguing the decision lacked a sufficient legal or rational foundation.
The related idea of arbitrary power refers to using authority without appropriate limits or without adequately considering other people’s rights or interests. Oxford and Cambridge both recognize this formal sense of the word.
Important: In legal writing, arbitrary can have a more technical meaning than it does in ordinary conversation. Its exact significance depends on the applicable law and context.
What Does Arbitrary Mean in Math?
In mathematics, arbitrary can be used somewhat differently from its everyday meaning.
When a mathematician says “an arbitrary number”, it often means any number selected without restricting it to a particular value.
For example:
“Let be an arbitrary real number.”
This does not necessarily mean that xx was selected randomly. It means the statement is intended to apply to any real number that satisfies the stated conditions.
Example
If a proof says:
“For an arbitrary positive integer …”
it generally means the argument should work for any positive integer nn, not just a randomly selected one.
This is an important distinction because arbitrary in technical writing does not always carry the negative sense of “unreasonable.”
Arbitrary vs. Random
The words arbitrary and random are sometimes used interchangeably, but they are not always identical.
| Word | General meaning | Example |
|---|---|---|
| Arbitrary | Chosen without a clear reason, rule, or consistent basis | “The deadline seems arbitrary.” |
| Random | Determined by chance rather than a predictable selection process | “A random number generator selected the winner.” |
| Accidental | Happening unintentionally | “The mistake was accidental.” |
| Haphazard | Done without organization or planning | “The files were arranged haphazardly.” |
Cambridge lists random, chance, and haphazard among words related to the chance-based sense of arbitrary, while also distinguishing their usage.
A useful distinction
Random often emphasizes chance.
Arbitrary often emphasizes lack of a clear reason, rule, or justification.
For example:
- A lottery winner is selected randomly.
- A manager choosing an employee based on an unexplained personal preference may be making an arbitrary decision.
Arbitrary Synonyms
Depending on the context, synonyms for arbitrary include:
- Random
- Unreasoned
- Unjustified
- Unsystematic
- Haphazard
- Capricious
- Subjective
- Personal
- Unpredictable
- Whimsical
- Inconsistent
- Chance-based
However, these words are not perfect substitutes in every sentence.
For example, random emphasizes chance, while unjustified emphasizes the absence of adequate reasoning.
Cambridge’s thesaurus includes words such as random, subjective, personal, capricious, inconsistent, and unrestrained among terms related to different senses of arbitrary.
Arbitrary Antonyms
Common opposites of arbitrary include:
- Reasonable
- Rational
- Logical
- Objective
- Justified
- Systematic
- Consistent
- Deliberate
- Planned
- Principled
- Fair
Example
Arbitrary:
“The rules were changed for no clear reason.”
Reasonable:
“The rules were changed after reviewing safety concerns.”
The second decision has a stated basis, so it is less likely to be described as arbitrary.
How to Use “Arbitrary” in a Sentence
Here are natural examples for everyday and formal writing:
Everyday English
- “That seems like an arbitrary choice.”
- “Why did you pick that number? Was it arbitrary?”
- “The deadline appears completely arbitrary.”
- “They used an arbitrary method to select the winner.”
Academic writing
- “The researchers used an arbitrary starting point.”
- “The division between the two categories is somewhat arbitrary.”
- “An arbitrary value was assigned to the variable.”
Business writing
- “Employees were concerned about the arbitrary nature of the new policy.”
- “The pricing rule appears arbitrary and inconsistent.”
- “We should establish clear criteria instead of making arbitrary decisions.”
Formal or legal contexts
- “The decision was challenged as arbitrary.”
- “Officials should not exercise arbitrary power.”
- “The policy was criticized for its arbitrary application.”
Arbitrary vs. Unreasonable
These words are related but not identical.
Arbitrary suggests that something lacks a clear, consistent, or rational basis.
Unreasonable means that something is not sensible, fair, or acceptable when judged against the circumstances.
A decision can be unreasonable because it produces a poor result, while an arbitrary decision may be criticized because there is no adequate explanation or consistent basis for making it.
Example
A company might make an unpopular but well-reasoned decision. That decision could be controversial without necessarily being arbitrary.
On the other hand, a company that applies a rule differently to similar employees without explaining why may be accused of acting arbitrarily.
Arbitrary vs. Subjective
Subjective means influenced by personal opinions, feelings, tastes, or perspectives.
Arbitrary usually goes further by suggesting that a choice lacks a sufficient reason, consistent standard, or rational basis.
For example:
“Choosing your favorite movie is subjective.”
That does not necessarily mean the choice is arbitrary.
But:
“The manager selected the employee without considering any qualifications.”
That could be described as arbitrary.
So, subjective does not automatically mean arbitrary
Common Phrases With “Arbitrary”
You may encounter arbitrary in several common expressions:
1. Arbitrary decision
A decision made without a clear or reasonable basis.
Example:
“The committee’s arbitrary decision surprised everyone.”
2. Arbitrary rule
A rule that appears to lack a meaningful justification.
Example:
“Employees questioned the arbitrary rule.”
3. Arbitrary number
A number selected without a special reason, particularly in technical or mathematical contexts.
Example:
“Choose an arbitrary number between 1 and 100.”
4. Arbitrary choice
A selection made without a clear determining principle.
Example:
“The color was an arbitrary choice.”
5. Arbitrary power
Authority exercised without appropriate limits or regard for other people’s rights or interests.
Example:
“The constitution was intended to limit arbitrary power.”
6. Arbitrary decision-making
A process in which choices appear to be made according to personal preference, chance, or inconsistent standards rather than established criteria.
What Does “Arbitrarily” Mean?
Arbitrarily is the adverb form of arbitrary.
It means in a way that is based on chance, personal choice, or an insufficiently explained decision rather than a clear reason or system.
Examples
- “They arbitrarily selected three applicants.”
- “The rules cannot be changed arbitrarily.”
- “The manager arbitrarily changed the schedule.”
- “The number was chosen arbitrarily.”
Compare:
Arbitrary:
“The selection was arbitrary.”
Arbitrarily:
“They selected the candidates arbitrarily.”
What Does “Arbitrariness” Mean?
Arbitrariness is the noun form.
It refers to the quality or condition of being arbitrary.
For example:
“The arbitrariness of the policy caused concern among employees.”
In this sentence, arbitrariness describes the policy’s lack of a clear, consistent, or sufficiently justified basis. Oxford recognizes this noun as referring to the quality of not seeming to be based on a reason, system, or plan.
Word forms
| Word | Part of speech | Meaning |
|---|---|---|
| Arbitrary | Adjective | Not based on a clear reason or system |
| Arbitrarily | Adverb | In an arbitrary manner |
| Arbitrariness | Noun | The quality of being arbitrary |
How to Remember the Meaning of Arbitrary
A simple memory trick is:
Arbitrary = “No clear reason.”
When you see the word in a sentence, ask:
“Why was this choice made?”
If the answer is essentially “There is no clear reason; someone simply chose it,” arbitrary may be an appropriate word.
Remember, however, that in mathematics and other technical contexts, arbitrary can simply mean any value or object chosen without restricting it to a particular one.
Is Arbitrary Always Negative?
No.
In ordinary conversation, arbitrary often has a negative or critical tone because it can suggest that a decision is unreasonable, unfair, or poorly justified.
For example:
“The company imposed an arbitrary rule.”
That sounds critical.
But in mathematics:
“Let be an arbitrary real number.”
There is usually no negative judgment. It simply means that can be any real number under consideration.
Therefore, the meaning of arbitrary depends heavily on context.
Quick Summary of Arbitrary Meaning
| Question | Answer |
|---|---|
| What does arbitrary mean? | Based on personal choice, chance, or an insufficiently clear reason or system. |
| Is arbitrary the same as random? | Sometimes, but not always. Arbitrary often emphasizes the lack of a clear basis. |
| Is arbitrary negative? | Often in everyday use, but not necessarily in technical contexts. |
| What is an arbitrary decision? | A decision made without a clear, consistent, or adequately justified basis. |
| What is arbitrary in math? | Often means any value or object chosen without restricting it to a particular one. |
| What is arbitrarily? | The adverb form of arbitrary. |
| What is arbitrariness? | The quality of being arbitrary. |
FAQs
Arbitrary means chosen or decided without a clear, logical, or consistent reason. It can also describe something determined by chance or personal preference.
Not always. Random primarily refers to chance, while arbitrary can refer to a choice made without a clear reason, rule, or justification. The two words overlap in some contexts.
If a manager chooses one qualified employee for a promotion solely because they personally prefer that employee, without using relevant criteria, the decision could be described as arbitrary.
It is usually neutral-to-negative in everyday English, especially when describing a rule or decision as unreasonable or unjustified. In mathematics and other technical contexts, it can be neutral.
Depending on context, synonyms include random, subjective, haphazard, unreasoned, unjustified, capricious, personal, and inconsistent.
Common antonyms include reasonable, rational, objective, justified, systematic, consistent, deliberate, and principled.
In mathematics, arbitrary commonly means any value or object that meets the stated conditions, rather than one particular predetermined value.
Subjective means influenced by personal opinion or perspective. Arbitrary generally suggests that a choice lacks a clear, consistent, or adequately justified basis. A subjective choice is not necessarily arbitrary.
Conclusion
The arbitrary meaning is easiest to understand as “chosen or decided without a clear, logical, or consistent reason.” The word can describe a random-looking choice, an unexplained rule, an inconsistent decision, or—in formal contexts—the use of power without appropriate limits.
For example, “The rule seems arbitrary” means the rule appears to have been created without a clear or reasonable basis.
The important thing to remember is that arbitrary changes slightly with context. In everyday English, it often carries a critical meaning, while in mathematics, “an arbitrary number” can simply mean any number that satisfies the relevant conditions.
If you’re learning English vocabulary, focus on the central idea: arbitrary choices lack an obvious or established basis. Once you understand that idea, the word becomes much easier to recognize and use correctly.
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