Longman Dictionary of Contemporary English
variable
I.adjectiveWikipedia
Variable
Variable may refer to:
 Variable (research), a logical set of attributes
 Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many sciences
 Variable (computer science), a symbolic name associated with a value and whose associated value may be changed
 Dependent and independent variables in statistics
Variable (mathematics)
In elementary mathematics, a variable is an alphabetic character representing a number, called the value of the variable, which is either arbitrary or not fully specified or unknown. Making algebraic computations with variables as if they were explicit numbers allows one to solve a range of problems in a single computation. A typical example is the quadratic formula, which allows one to solve every quadratic equation by simply substituting the numeric values of the coefficients of the given equation to the variables that represent them.
The concept of variable is also fundamental in calculus. Typically, a function involves two variables, and , representing respectively the value and the argument of the function. The term "variable" comes from the fact that, when the argument (also called the "variable of the function") varies, then the value varies accordingly.
In more advanced mathematics, a variable is a symbol that denotes a mathematical object, which could be a number, a vector, a matrix, or even a function. In this case, the original property of "variability" of a variable is not kept (except, sometimes, for informal explanations).
Similarly, in computer science, a variable is a name (commonly an alphabetic character or a word) representing some value represented in computer memory. In mathematical logic, a variable is either a symbol representing an unspecified term of the theory, or a basic object of the theory, which is manipulated without referring to its possible intuitive interpretation.
Variable (computer science)
In computer programming, a variable or scalar is a storage location paired with an associated symbolic name (an identifier), which contains some known or unknown quantity of information referred to as a value. The variable name is the usual way to reference the stored value; this separation of name and content allows the name to be used independently of the exact information it represents. The identifier in computer source code can be bound to a value during run time, and the value of the variable may thus change during the course of program execution.
Variables in programming may not directly correspond to the concept of variables in mathematics. The value of a computing variable is not necessarily part of an equation or formula as in mathematics. In computing, a variable may be employed in a repetitive process — assigned a value in one place, then used elsewhere, then reassigned a new value and used again in the same way (see iteration). Variables in computer programming are frequently given long names to make them relatively descriptive of their use, whereas variables in mathematics often have terse, one or twocharacter names for brevity in transcription and manipulation.
A variable storage location may be referred by several different identifiers, a situation known as aliasing. Assigning a value to the variable using one of the identifiers will change the value that can be accessed through the other identifiers.
Compilers have to replace variables' symbolic names with the actual locations of the data. While a variable's name, type, and location often remain fixed, the data stored in the location may be changed during program execution.
The Collaborative International Dictionary
Variable
Variable \Va"ri*a*ble\, n.
That which is variable; that which varies, or is subject to change.
(Math.) 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 x^ 2  y^ 2 = R^ 2, x and y are variables.

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

pl. Those parts of the sea where a steady wind is not expected, especially the parts between the tradewind belts.
Independent variable (Math.), that one of two or more variables, connected with each other in any way whatever, to which changes are supposed to be given at will. Thus, in the equation x^ 2  y^ 2 = R^ 2, if arbitrary changes are supposed to be given to x, then x is the independent variable, and y is called a function of x. There may be two or more independent variables in an equation or problem. Cf. Dependent variable, under Dependent.
Variable
Variable \Va"ri*a*ble\, a. [L. variabilis: cf. F. variable.]
Having the capacity of varying or changing; capable of alternation in any manner; changeable; as, variable winds or seasons; a variable quantity.

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.
Shak.His heart, I know, how variable and vain!
Milton.Variable exhaust (Steam Eng.), a blast pipe with an adjustable opening.
Variable quantity (Math.), a variable.
Variable stars (Astron.), fixed stars which vary in their brightness, usually in more or less uniform periods.
Syn: Changeable; mutable; fickle; wavering; unsteady; versatile; inconstant.
Wiktionary
variable
a. 1 Able to vary. 2 Likely to vary. 3 Marked by diversity or difference. 4 (context mathematics English) Having no fixed quantitative value. 5 (context biology English) Tending to deviate from a normal or recognized type. n. 1 Something that is #Adjective. 2 Something whose value may be dictated or discovered.
WordNet
variable
adj. liable to or capable of change; "rainfall in the tropics is notoriously variable"; "variable winds"; "variable expenses" [ant: invariable]
marked by diversity or difference; "the varying angles of roof slope"; "nature is infinitely variable" [syn: varying]
(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"
n. something that is likely to vary; something that is subject to variation; "the weather is one variable to be considered"
a quantity that can assume any of a set of values [syn: variable quantity]
a star that varies noticeably in brightness [syn: variable star]
a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity
Douglas Harper's Etymology Dictionary
variable
late 14c., of persons, "apt to change, fickle," from Old French variable "various, changeable, fickle," from Late Latin variabilis "changeable," from variare "to change" (see vary). Of weather, seasons, etc., attested from late 15c.; of stars, from 1788.
variable
"quantity that can vary in value," 1816, from variable (adj.) in mathematical sense of "quantitatively indeterminate" (1710). Related: Variably; variability.
Usage examples of "variable".
Chapter VII Instinct Instincts comparable with habits, but different in their origin  Instincts graduated  Aphides and ants  Instincts variable  Domestic instincts, their origin  Natural instincts of the cuckoo, ostrich, and parasitic bees  Slavemaking ants  Hivebee, its cellmaking instinct   Difficulties on the theory of the Natural Selection of instincts  Neuter or sterile insects  Summary.
And yet, there was nothing surprising in that, for everything is variable in the austral seas.
There are three key variables that will define this struggle, variables that act in the realm between the common and the singular, between the axiomatic of command and the selfidentification of the subject, and between the production of subjectivity by power and the autonomous resistance of the subjects themselves.
My previous tests have been made too late to learn the exact rate of coagulation, which may be variable.
It contains five million three hundred thousand cryotrons and is capable of dealing simultaneously with over one hundred thousand variables.
The one thing which everywhere is variable and evanescent, is evil, or the imperfect adjustment of the creature with the works and designs of the Creator.
It was obviously encrypted, but what sort of a code: logarithmic, exponential, random, or variable sequential?
The variable opulence of some of her new friends caused a forest of ambitious ideas to spring up in the mind of Mademoiselle Mimi, who up until then had only had modest tastes, and was content with the necessaries of life that Rodolphe did his best to procure for her.
Through the use of phenothiazine spansules he realized, which act over a period of hours at a variable rate.
VARIABLE BALLAST TANKS Tanks used to hold seawater for added weight, or conversely, seawater tanks that can be pumped out or blown out to lighten the ship.
Through the social development of capital, the mechanisms of modern sovereigntythe processes of coding, overcoding, and recoding that imposed a transcendent order over a bounded and segmented social terrainare progressively replaced by an axiomatic: that is, a set of equations and relationships that determines and combines variables and coefficients immediately and equally across various terrains without reference to prior and fixed definitions or terms.
This is a subacute or chronic form of inflammation of the mucous membrane of the bronchial tubes, of a very persistent character and variable intensity.
To accept uploading, that, too, is wrong in her mind: She will not admit her identity is a variable, not a constant.
To accept uploading, that, too, is wrong in her mind: she will not admit her identity is a variable, not a constant.
The action of these vortices is proved to be of variable force, whether arising from atmospheric conditions, or due to an increased activity of the ethereal medium throughout the whole system, is at present immaterial.