dependent variable

factor whose value is influenced by other variables

In mathematics, an independent variable is any of the arguments, i.e. "inputs", to a function. These are contrasted with the dependent variable, which is the value, i.e. the "output", of the function. Thus if we have a function f(x), then x is an independent variable, and f(x) is a dependent variable. The dependent variable depends on the independent variables; hence the names.
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Noun
1. (statistics) a variable in a logical or mathematical expression whose value depends in the independent variable; if f(x)=y, y is the dependent variable
(hypernym) variable, variable quantity
(classification) statistics

in research; usually denoted as y, is a variable that is influenced to some extent by one or more other (independent) variables (see independent variable).

The terms dependent and independent variable apply mostly to experimental research where some variables are manipulated, and in this sense they are "independent" from the initial reaction patterns, features, intentions, etc. of the subjects. Some other variables are expected to be "dependent" on the manipulation or experimental conditions. That is to say, they depend on "what the subject will do" in response. Independent variables are those that are manipulated whereas dependent variables are only measured or registered.
Somewhat contrary to the nature of this distinction, these terms are also used in studies where we do not literally manipulate independent variables, but only assign subjects to "experimental groups" based on some preexisting properties of the subjects. For example, if in an experiment, males are compared with females regarding their white cell count (WCC), Gender could be called the independent variable and WCC the dependent variable.
See Dependent vs. independent variables for more information.