The adjective variable is used to describe something that is liable to change often, such as the weather, interest rates, or your teacher's mood.

If you mention the noun variable to people who are math-phobic, you may give them nightmares because they don't like to think about numbers or values that can change in equations. The adjective form of variable has been around since the late 1300s, applying first to people, and then, in the late 1400s, to weather. The noun form first appeared in Lacroix's Differential and Integral Calculus in 1816, guaranteeing that math students would be solving for the variable x for generations to come.

Definitions of variable

n something that is likely to vary; something that is subject to variation

“the weather is one variable to be considered”
Type of:
a separate and self-contained entity

n a quantity that can assume any of a set of values

variable quantity
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a variable in a logical or mathematical expression whose value determines the dependent variable; if f(x)=y, x is the independent variable
experimental variable, independent variable
(statistics) a variable whose values are independent of changes in the values of other variables
correlate, correlative
either of two or more related or complementary variables
degree of freedom
(statistics) an unrestricted variable in a frequency distribution
dependent variable
(statistics) a variable in a logical or mathematical expression whose value depends on the independent variable
predictor variable
a variable that can be used to predict the value of another variable (as in statistical regression)
(mathematics) a variable that has zero as its limit
chance variable, random variable, stochastic variable, variant, variate
a variable quantity that is random
a variable quantity that cannot be resolved into components
a generalization of the concept of a vector
a variable quantity that can be resolved into components
an independent variable in statistics
cross product, vector product
a vector that is the product of two other vectors
resultant, vector sum
a vector that is the sum of two or more other vectors
radius vector
a line connecting a point in space to the origin of a polar coordinate system
radius vector
a line connecting a satellite to the center of the body around which it is rotating
Type of:
the concept that something has a magnitude and can be represented in mathematical expressions by a constant or a variable

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

a symbol in a logical or mathematical expression that can be replaced by the name of any member of specified set
unknown, unknown quantity
a variable whose values are solutions of an equation
Type of:
an arbitrary sign (written or printed) that has acquired a conventional significance

n a star that varies noticeably in brightness

variable star
North Star
the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it
Type of:
(astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior

adj marked by diversity or difference

“nature is infinitely variable
characterized by variety

adj liable to or capable of change

“rainfall in the tropics is notoriously variable
variable winds”
variable expenses”
displaying a lack of consistency
likely to change frequently often without apparent or cogent reason; variable
changeable, uncertain, unsettled
subject to change
changing so that interrelations with another variable quantity or set of quantities remain unchanged
pertaining to any procedure involving two or more variables
taking on different forms
continuously varying
exhibiting variation and change
changeable or inconstant
not liable to or capable of change
(sometimes followed by `with') in agreement or consistent or reliable
steadfast in purpose or devotion or affection
changeless, constant, invariant, unvarying
unvarying in nature
hard-and-fast, strict
(of rules) stringently enforced
unaffected by a designated operation or transformation
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adj (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”
capable of adapting (of becoming or being made suitable) to a particular situation or use

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