# What is diameter?

A diameter is a segment that connects two points of a circle and passes through its center. Let us consider in more detail what diameter is and in what sciences this term is used.

Thus, the astronomical and mathematical concepts of diameter are distinguished.

## Diameter in mathematics

In mathematics, diameter is also consideredthe transverse line of any round or seemingly circular body. It should be noted that this concept admits certain generalizations and extends to other objects having geometric forms. There is a diameter of a graph, a geometric figure, a set M lying in a metric space, and so on.

To calculate the diameter of a circle, there arespecial mathematical formulas. In particular, the radius is half the diameter. Knowing this measure, you can calculate the entire length of the segment. Another way is to measure the diameter with the help of the circumference. This indicator must be divided by the number Pi, which is 3.14.

## Astronomical Diameter

The diameter of the luminary in astronomical science is:

- true, which is the diameter of the cosmic body in a linear measure;
- visible, serving as a measure of the angle under which the planet is visible, it is measured in degrees and fractions.

This concept is used exclusively in astronomy and is a professional term.