independent variable

[ in-di-pen-duhnt vair-ee-uh-buhl ]
/ ˈɪn dɪˌpɛn dənt ˈvɛər i ə bəl /
Save This Word!

Definition of independent variable

Mathematics. a variable in a functional relation whose value determines the value or values of other variables, as x in the relation y = 3x2.Compare dependent variable (def. 1).
Statistics. (in an experiment) a variable that is intentionally changed to observe its effect on the dependent variable.Compare dependent variable (def. 2), control variable (def. 1).


Click for a side-by-side comparison of meanings. Use the word comparison feature to learn the differences between similar and commonly confused words.
We have a challenge that will make you blush: do you know the many words and ways to describe the opposite of red?
Question 1 of 7
Which of the following colors is used to symbolize AIR?

Origin of independent variable

First recorded in 1850–55
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is an independent variable?

In the context of scientific experiments, an independent variable is a factor that you change to see how it affects the results.

So, for instance, if you’re measuring how effective a medication is, independent variables could include the amount of dosage, how frequently it’s taken, and the characteristics of each test subject, such as their age and weight.

In general, a variable is called a variable because it can vary. It’s any factor that could change or be changed. In the context of scientific experiments, there are three different types of variables: dependent variables, independent variables, and control variables. Independent variables are the factors that you change. Dependent variables are things that are affected by the changes that you make—the results of the tests (which depend on the independent variables). Control variables are the factors that you do not change. They are kept the same for every test or measurement in order to make sure that the results can be compared fairly.

For example, let’s say you’re trying to figure out which brand of plant food will help a sunflower grow to the tallest height. The dependent variable is the final height of the sunflower. The independent variable (the factor that you change) is the brand of plant food. There are a number of other factors that could impact the growth of the plant, including things like the amount of sunlight and the amount of water. To allow for a proper comparison of the results, these need to be control variables—they need to be controlled, or kept the same. This way, you can have a greater degree of certainty that the final difference in heights (the dependent variable) is due to which food each sunflower received (the independent variable), not differences in sunlight or water.

Why are independent variables important?

Science is messy. We like to think of experimentation as a simple process of “change one thing and record what happens,” but in reality, every possible subject of study has dozens of different factors that can impact the results—the variables. The one thing that you change is the independent variable.

Scientists are trained to be careful when setting all the variables for an experiment. It’s especially important to keep track of the independent variables so you know how you arrived at the results that you did.

Understanding the importance of variables will make you more likely to draw sound conclusions and less likely to fall for claims based on faulty science. For example, when examining suspicious statistics or experiment results, a good place to start is to ask what independent variables were involved—what was changed to get the results.

Did you know … ?

The term independent variable is used in the context of formal scientific experiments, but you use the same concept all the time without thinking about it. The process of trial and error involves trying new methods of doing something until you get the results you want. The new methods are the independent variables and the results of each attempt are the dependent variables.

What are real-life examples of independent variables?

Independent variables are crucial elements of any experiment, regardless of what is being studied.


What other words are related to independent variable?

Quiz yourself!

True or False? 

In an experiment, the independent variable is the one that you change.

How to use independent variable in a sentence

British Dictionary definitions for independent variable

independent variable

Also called: argument a variable in a mathematical equation or statement whose value determines that of the dependent variable: in y = f(x), x is the independent variable
Also called: predictor statistics the variable which an experimenter deliberately manipulates in order to observe its relationship with some other quantity, or which defines the distinct conditions in an experimentSee also experimental condition
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for independent variable

independent variable
[ ĭn′dĭ-pĕndənt ]

In mathematics, a variable whose value determines the value of other variables. For example, in the formula for the area of a circle, A = πr2, r is the independent variable, as its value determines the value of the area (A). Compare dependent variable.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.