Difference (science)

A difference is a concept expressing the distinction between two things, two numbers, or two states. In mathematics, a difference is the result of subtraction: when one number is subtracted from another, the amount that remains is called the difference. For example, the difference between 9 and 4 is 5.

In broader science, the term difference is used more widely. It is defined as the distinguishing features between two types, two groups, or two measurements. The method involves selecting a measurement that can be standardized, then comparing the values obtained from two different conditions.

Difference in mathematics

In mathematics, difference is tied to the operation of subtraction. If a and b are compared, the straightforward difference is a minus b. When only the magnitude of the separation is desired, without regard to whether a number is positive or negative, the absolute value is used. Thus the difference between 3 and 7 is 4, regardless of the order.

Difference in measurement and experimentation

In experimental science, the difference between two measurements is evaluated taking measurement error into account. Each measurement has a small margin of uncertainty that cannot be avoided. If the difference is smaller than that error, researchers typically consider it indistinguishable. If the difference is larger, it is regarded as indicating a genuine distinction.

Difference in classification

In life sciences and social sciences, difference is used to distinguish groups. The features used for classification must be measurable and reproducible. Variation within a single group (internal difference) is compared to variation between groups, to determine whether the classification rests on solid evidence.