**Coefficient** is synonymous with **figure, factor or proportion**. **etymologically**is composed of the Latin prefix *cum*which means ‘with’, and *efficients*which derives from the verb of *effecere*, and translates ‘to do’, ‘to work’. For this reason, in certain contexts, it works as an adjective that refers to something that, together with something else, contributes to producing a certain effect.

In **Math**for instance, **coefficient is a multiplicative factor**, that is, the constant number that is found to the left of a variable or unknown and multiplies it. For example, 3X = X + X + X, where 3 is **coefficient** of the variable X.

In **Physical**the **coefficient** it’s a **numerical value** that indicates the degree or intensity of a certain property or characteristic, be it of a body or of a phenomenon.

Inside of **Psychology**, **coefficient** it can also refer to a measurement of a person’s reasoning abilities to estimate their IQ (see IQ here).

## Coefficient of variation

In **Statistics**the **coefficient of variation** is a measurement used to analyze the relationship between the standard deviation of a sample and its arithmetic mean, all with the purpose of finding the relative dispersion. In this sense, the **coefficient of variation** it is a way of expressing the variability of the data, leaving out the influence of the order of the dimensions in the variable, but considering the proportion between the means and the standard deviation.

## Correlation coefficient

The **Pearson’s correlation coefficient** (named after Karl Pearson, who formulated it) is a measure used in **Statistics** to calculate the degree of linear relationship between two random variables, therefore, it is also known as **linear correlation coefficient**.

## Coefficient of friction

In **Physical**the **coefficient of friction**also called **coefficient of friction**, indicates the opposition to sliding offered by the surfaces of two bodies in contact. In this sense, there are two types of friction coefficients: the static one, that is, the one of two surfaces at rest, where no movement is registered, and the dynamic one, which is when both surfaces are in relative movement, one with respect to the other. The coefficient of friction is usually expressed by the Greek letter μ.

## Expansivity

What **expansivity** is called, in **Physical**, the quotient obtained from the measurement of the relative change in length or volume experienced by a body, whether it is in a solid, liquid or gaseous state, when it is subjected to a change in temperature, which may be ascending or descending. In this sense, the increase in temperature will be proportional to the expansion, be it linear, superficial or volumetric.

### Linear expansion coefficient

The **linear expansion coefficient** measures the variations in the dimension of solid bodies (be it the width, length or height of the body, never more than one) when they are subjected to changes in temperature.

### Surface expansion coefficient

The **surface expansion coefficient** we also find it in solid surfaces, which expand or contract according to the variation in temperature, and it is recorded in two dimensions. In this sense, this type of expansion coefficient varies the total area of the surface, since it occurs in two dimensions.

### Volumetric expansion coefficient

The **volumetric expansion coefficient** It is used to calculate the volume variations (that is, in three dimensions) that occur on solid, gaseous or liquid surfaces, when changes in temperature cause the body to contract or expand.