Definition: A parameter is a number that can be considered as a constant for a particular instance while it can vary with the underlying circumstance for which it is used.

Examples of  parameters include physical constants that depend on the particular matter involved, such as the atomic mass of an element or compound, or a location, such as the acceleration due to the gravitational force on a planet or satellite.
Time is often considered as a parameter in considering an otherwise static measurement, such as position or temperature of an object or price or value of a commodity or service.

See Parameter in Wikipedia.