# Constant vs. Variable — What's the Difference?

By Tayyaba Rehman — Published on September 16, 2023
A constant remains unchanged over time, while a variable is subject to change. Constant denotes stability and permanence and variable implies dynamism and change.

## Key Differences

In the realms of mathematics and science, a constant represents a value that does not change. Once its value is defined, it remains fixed for the entirety of the discussion or experiment. Conversely, a variable stands as a symbol that can represent different values; it varies based on conditions or equations.
While the term constant denotes stability and permanence, the term variable implies dynamism and change. A constant's primary characteristic is its unwavering nature, whether in mathematical equations, scientific experiments, or everyday scenarios. On the other hand, the essence of a variable is its flexibility and adaptability.
Take a scientific experiment as an instance: when studying the effect of light on plant growth, if the amount of water given to each plant remains the same throughout the experiment, it is a constant. Meanwhile, the amount of light, if it changes for different groups of plants, becomes the variable.
In programming, a constant might refer to a value that a developer decides should not be altered as the code executes, ensuring consistency. In contrast, a variable in programming holds data that can change as the program runs, offering flexibility.

## Comparison Chart

### Definition

A value that does not change.
A symbol that can represent different values.

### Nature

Unchanging.
Subject to change.

### Usage

Represents fixed values in equations.
Holds changeable data in equations.

### Example Scenario

Water amount in a plant experiment.
Light exposure in a plant experiment.

### Role in Programming

Value not altered during code execution.
Holds data that can change during execution.

## Compare with Definitions

#### Constant

Permanent and unvarying.
His constant dedication to the project ensured its success.

#### Variable

A symbol representing an unknown value in mathematics.
In the equation x + 5 = 10, x is the variable.

#### Constant

Not changing or varying; continuous
A constant gentle rain.
Drove at a constant speed.

#### Variable

An element or factor that can change.
In our experiment, temperature was the main variable.

#### Constant

Happening regularly or repeatedly; continual
The constant barking of the dog next door.
Constant interruptions.

#### Variable

Likely to change or vary; subject to variation; changeable.

#### Constant

Unchanging in nature, value, or extent; invariable
A constant wind speed.

#### Variable

Inconstant; fickle.

#### Constant

Steadfast in purpose, loyalty, or affection; faithful
A constant friend.

#### Variable

(Biology) Tending to exhibit genetic variation or variation in a physical trait
Geographically variable color patterns.

#### Constant

Something that is unchanging or invariable.

#### Variable

(Mathematics) Having no fixed quantitative value.

#### Constant

A quantity assumed to have a fixed value in a specified mathematical context.

#### Variable

Something that varies or is prone to variation.

#### Constant

An experimental or theoretical condition, factor, or quantity that does not vary or that is regarded as invariant in specified circumstances.

#### Variable

(Astronomy) A variable star.

#### Constant

Unchanged through time or space; permanent.

#### Variable

A quantity capable of assuming any of a set of values.

#### Constant

Consistently recurring over time; persistent.

#### Variable

A symbol representing such a quantity. For example, in the expression a2 + b2 = c2, a,b, and c are variables.

#### Constant

Steady in purpose, action, feeling, etc.

#### Variable

Able to vary or be varied.
Variable winds or seasons; a variable quantity; a variable resistor

#### Constant

Firm; solid; not fluid.

Likely to vary.

#### Constant

(obsolete) Consistent; logical.

#### Variable

Marked by diversity or difference.

#### Constant

Bounded above by a constant.
Constant time
Constant space

#### Variable

(mathematics) Having no fixed quantitative value.

#### Constant

That which is permanent or invariable.

#### Variable

(biology) Tending to deviate from a normal or recognized type.

#### Constant

(algebra) A quantity that remains at a fixed value throughout a given discussion.

#### Variable

Something that is variable.

#### Constant

(science) Any property of an experiment, determined numerically, that does not change under given circumstances.

#### Variable

Something whose value may be dictated or discovered.
There are several variables to consider here.

#### Constant

(computing) An identifier that is bound to an invariant value; a fixed value given a name to aid in readability of source code.

#### Variable

(mathematics) A symbol representing a variable.

#### Constant

Firm; solid; fixed; immovable; - opposed to fluid.
If . . . you mix them, you may turn these two fluid liquors into a constant body.

#### Variable

(programming) A named memory location in which a program can store intermediate results and from which it can read them.

#### Constant

Not liable, or given, to change; permanent; regular; continuous; continually recurring; steadfast; faithful; not fickle. Opposite of changeable and variable.
Both loving one fair maid, they yet remained constant friends.
I am constant to my purposes.
His gifts, his constant courtship, nothing gained.
Onward the constant current sweeps.

#### Variable

(astronomy) A variable star.

#### Constant

Remaining unchanged or invariable, as a quantity, force, law, etc.

#### Variable

(nautical) A shifting wind, or one that varies in force.

#### Constant

Consistent; logical.

#### Variable

Those parts of the sea where a steady wind is not expected, especially the parts between the trade-wind belts.

#### Constant

That which is not subject to change; that which is invariable.

#### Variable

Having the capacity of varying or changing; capable of alternation in any manner; changeable; as, variable winds or seasons; a variable quantity.

#### Constant

A quantity that does not change its value; - used in countradistinction to variable.

#### Variable

Liable to vary; too susceptible of change; mutable; fickle; unsteady; inconstant; as, the affections of men are variable; passions are variable.
Lest that thy love prove likewise variable.
His heart, I know, how variable and vain!

#### Constant

A number whose value, when ascertained (as by observation) and substituted in a general mathematical formula expressing an astronomical law, completely determines that law and enables predictions to be made of its effect in particular cases.

#### Variable

That which is variable; that which varies, or is subject to change.

#### Constant

A number expressing some property or condition of a substance or of an instrument of precision; as, the dielectric constant of quartz; the collimation constant of a transit instrument.

#### Variable

A quantity which may increase or decrease; a quantity which admits of an infinite number of values in the same expression; a variable quantity; as, in the equation x2 - y2 = R2, x and y are variables.

#### Constant

A data structure that does not change during the course of execution of a program. It may be a number, a string, or a more complex data structure; - contrasted with variable.

#### Variable

A shifting wind, or one that varies in force.

#### Constant

A quantity that does not vary

#### Variable

Something that is likely to vary; something that is subject to variation;
The weather is one variable to be considered

#### Constant

A number representing a quantity assumed to have a fixed value in a specified mathematical context;
The velocity of light is a constant

#### Variable

A quantity that can assume any of a set of values

#### Constant

Persistent in occurrence and unvarying in nature;
Maintained a constant temperature
A constant beat
Principles of unvarying validity

#### Variable

A star that varies noticeably in brightness

#### Constant

Continually recurring or continuing without interruption;
Constant repetition of the exercise
Constant chatter of monkeys

#### Variable

A symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity

#### Constant

Steadfast in purpose or devotion or affection;
A man constant in adherence to his ideals
A constant lover
Constant as the northern star

#### Variable

Liable to or capable of change;
Rainfall in the tropics is notoriously variable
Variable winds
Variable expenses

#### Constant

Uninterrupted in time and indefinitely long continuing;
The ceaseless thunder of surf
In constant pain
Night and day we live with the incessant noise of the city
The never-ending search for happiness
The perpetual struggle to maintain standards in a democracy
Man's unceasing warfare with drought and isolation
Unremitting demands of hunger

#### Variable

Marked by diversity or difference;
The varying angles of roof slope
Nature is infinitely variable

#### Constant

A value that remains the same over time.
The speed of light in a vacuum is a universal constant.

#### Variable

(used of a device) designed so that a property (as e.g. light) can be varied;
A variable capacitor
Variable filters in front of the mercury xenon lights

#### Constant

Something that remains unchanged in equations.
In the equation E=mc^2, c is the constant representing the speed of light.

#### Variable

Something that differs or changes based on conditions.
Economic growth is a variable dependent on multiple factors.

#### Constant

Unchanging under different conditions.
No matter how much pressure you apply, the boiling point of water at sea level remains a constant.

#### Variable

Liable to vary or change.
Weather is a variable factor in outdoor planning.

#### Constant

Continual; regularly recurring.
Her constant chatter kept him entertained during the long drive.

#### Variable

Not consistent or having a fixed pattern.
The variable performance of the team led to unpredictable results.

## Common Curiosities

#### In what scenarios might a Variable be used?

Variables are used in mathematical equations, scientific experiments, and programming to represent changeable values.

#### What is a Constant?

A constant is a value that remains unchanged over time.

#### Can a Constant ever change?

By definition, a constant remains fixed and does not change.

#### Are there any famous Constants in science?

Yes, like the gravitational constant (G) or Planck's constant (h).

#### In algebra, how do we typically represent Variables?

Variables are usually represented by letters, such as x, y, or z.

#### Do all equations have both Constants and Variables?

Not necessarily. Some equations might only have constants, some only variables, and some both.

#### How do Variables enhance flexibility in equations?

Variables allow for different values to be plugged in, accommodating various scenarios or conditions.

#### Can a Variable become a Constant in different scenarios?

Yes, if a previously changeable value is fixed in a different context, it can act as a constant.

#### How is a Variable defined?

A variable is a symbol or element that can represent different values and is subject to change.

#### Why is it important to distinguish between Constant and Variable?

Distinguishing helps in understanding stability versus change in contexts like mathematical problems or scientific experiments.

#### Are there constants in programming?

Yes, constants in programming are values set to remain unchanged during the code's execution.

#### Is the term "constant" only used in mathematics and science?

No, it's used in everyday language to describe something unchanging or continual.

#### Why are Variables crucial in research?

Variables allow researchers to test hypotheses, study relations, and observe effects under varying conditions.

#### How do Constants contribute to the reliability of experiments?

By keeping certain elements constant, researchers can ensure that observed changes are due to the variable being tested.

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