variable
Noun pluralvariables
Pluralvariables
- 1Capable of varying, or of being varied by someone.
The thermostat keeps the room at a variable temperature throughout the day.
Membership fees here are variable and can be adjusted each year.
Similarchangeable, flexible, adjustable, alterable, modifiable
Oppositeconstant, unchangeable, invariable, immutable
Note
Built exactly as it looks: vary plus -able, which came through Old French from Latin variare, 'to change', and varius, 'different'. Like many -able words it points two ways. A variable wind changes of its own accord, while a variable resistor is one someone adjusts. Constant and invariable are its usual opposites.
- 2Inclined to change rather than stay the same.
Reception in this valley is variable, dropping out without warning.
Attendance at the lectures proved variable from week to week.
Similarunstable, fluctuating, inconstant, shifting, irregular
Oppositeconstant, steady, invariable, unchangeable
Note
Here change is a habit rather than a capacity, and the word moves toward character. Its neighbors are fickle, inconstant and unsteady. Shakespeare's Romeo and Juliet applies it to love: 'Lest that thy love prove likewise variable.' Said of a person, it sounds like an accusation. Said of reception or attendance, it is only a report. The capacity itself belongs to the 'able to change' sense.
- 3A quantity that can take any one of a set of possible values.
Each variable in the model can range over the real numbers.
By isolating one variable, the researchers measured its effect on growth.
Oppositeconstant
Note
Here the adjective has dropped its noun, so a variable quantity is simply a variable. Its defining partner is the constant, which holds one fixed value while the variable ranges over a set, such as the real numbers. The quantity and the letter that stands for it share the name, and mathematical writing moves between them freely.
- 4Lacking a single fixed numerical value.
The reaction proceeds at a variable rate depending on temperature.
Engineers designed the motor to run at variable speeds.
Similarchangeable, adjustable, fluctuating
Oppositeconstant, invariable
Note
Scientists and engineers use it for any quantity left open, and constant is its standard opposite. It sits most comfortably before a noun of rate or setting, as in a variable rate or a variable speed, and names something designed or observed to take different values. Used on its own as a noun, the same idea becomes the mathematical noun.
- 5A thing or factor whose nature or amount is open to change.
Mood is a variable that affects how people respond to questions.
When baking, oven temperature is the variable most likely to ruin a cake.
Similarfactor
Oppositeconstant, invariable
- 6A named location in memory where a program can store values and later read them back.
Assigning a value to a variable lets the function reuse it later.
The loop updates the counter variable on each pass.
Oppositeconstant
Note
Programming gives the mathematician's word a more physical meaning: a named slot whose contents a program can overwrite as it runs. You assign a value to a variable, read it back, or update it on each pass of a loop. Variables are typically typed and scoped to a particular block of code. That makes them closer to containers than to the mathematical quantity ranging over a set.
- 7A symbol, such as a letter, that stands for a quantity able to take different values.
Mathematicians often choose x or y as the variable in an equation.
Each variable in the formula is written as a single italic letter.
Oppositeconstant
Note
Notation turns the quantity into a mark on the page. By convention it is a single letter such as x, y or n, usually set in italics. Strictly speaking, the letter is the symbol and the quantity is what it stands for. The distinction matters when a text talks about its own notation, for example when it renames or substitutes one letter for another.
- 8Showing diversity, with differences from one case to the next.
The quality of the harvest was variable across the different fields.
Critics gave variable responses, some delighted and others unimpressed.
Similardiverse, varied, various, mixed, diversified
Oppositeunchanging
- 9A thing whose value can be either assigned or found out through investigation.
Treat demand as a variable to be discovered through market testing.
The committee fixed the budget, but staffing remained a variable to be settled later.
Similarparameter
Note
The researcher's everyday noun is most at home in the plural, as in 'several variables to consider.' Writing in American Scientist (2013), Katie L. Burke speaks of the ecological variables that may explain why bats harbor diseases that can infect humans. The field is often named in front of the noun. Parameter is the close synonym. Variable puts the stress on a value that is still open or unknown.
- 10Inclined to depart from the normal or established type.
The beetle's coloring is notably variable across its range.
Botanists found the flower's petal count to be variable within a single population.
Similaraberrant
Oppositeconstant, uniform, stable, invariable
Note
The biologist's sense describes a species or trait whose members stray from the recognized type, as a beetle's coloring may across its range. Aberrant is the near synonym. What separates it from the 'diverse' meaning is the norm. Here there is an established type to depart from, not just differences from one case to the next.
Less common meanings
- 11A star whose apparent brightness changes over time, as seen from Earth.
Each variable in the catalog is monitored for changes in brightness.
A famous variable in Cetus fades and recovers over roughly eleven months.
Note
Astronomers shorten variable star to just a variable, in the same way as the mathematical noun. A star's brightness may change through pulsation, through eruption, or through eclipse by a companion, and catalogs follow such stars over time. Within astronomy the short form needs no explanation. Elsewhere, the full phrase variable star avoids confusion with the mathematical sense.
- 12A wind that shifts direction or varies in force.
The log noted a variable through the afternoon, forcing constant trimming of the sails.
A southerly variable replaced the steady breeze by nightfall.
Note
Sailors turn the adjective into a name for the wind itself, so a ship's log can record 'a variable' through an afternoon. It is the opposite of the steady prevailing wind a navigator relies on to hold a course, and it demands constant trimming of the sails. In the plural the word names a place instead: the zones where such winds prevail.
- 13Regions of the sea where no steady wind can be relied upon, especially the belts lying between the trade winds.
The captain steered wide of the variables, knowing a steady wind was unlikely there.
After the trade winds died, the schooner entered a vast variable and lay becalmed for days.
Note
In this use the word is always plural: a ship sails into the variables. The belts between the trade winds are the chief example. In those calms, sailing vessels risked lying becalmed for long stretches. The singular keeps its own job as the shifting wind itself, so the number tells a reader whether a passage means a wind or a region.
Showing meanings only.
Practice
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Origin
English borrowed this word in the 14th century from Old French variable, which came from Latin variare ('to change'), from varius ('different, various'). It matches English vary plus -able.