Fundamentals of geometry

Geometry is a branch of mathematics that focuses on studying the properties and relationships of points, lines, angles, shapes, and the space they occupy. These concepts form the foundation of many branches of science and engineering, making geometry a crucial subject in academia and in practical applications. In this article, we will delve into the fundamentals of geometry, exploring the basic concepts and terminology that make up this essential field of study.

Points, Lines, and Planes

The foundation of geometry is built upon three basic entities - points, lines, and planes. A point is a location in space defined by its coordinates, usually represented on a graph as a "dot." A line is a straight path that extends indefinitely in both directions. A plane is a flat surface that extends infinitely in all directions. These entities are the building blocks of geometry, and all other geometrical concepts are defined in terms of these three entities.

Lines can be classified as either parallel, intersecting, or perpendicular. Parallel lines are lines that never intersect, while intersecting lines are lines that cross each other at a point. Perpendicular lines are lines that intersect at a right angle (90 degrees). These relationships between lines form the basis of many geometrical concepts, such as angles, triangles, and polygons.

Angles and Triangles

An angle is formed by two rays emanating from a common endpoint (vertex). The measure of an angle is usually given in degrees, with a full circle measuring 360 degrees. Angles can be classified as acute (less than 90 degrees), right (exactly 90 degrees), obtuse (greater than 90 degrees but less than 180 degrees), or straight (exactly 180 degrees).

Triangles are three-sided polygons that are formed by connecting three non-collinear points. Triangles can be classified based on their sides and angles. A triangle with three sides of equal length is called an equilateral triangle, while a triangle with two equal sides is called an isosceles triangle. A triangle with no equal sides is called a scalene triangle.

Triangles can also be classified based on their angles. A triangle with three acute angles is called an acute triangle, while a triangle with one right angle is called a right triangle. A triangle with one obtuse angle is called an obtuse triangle. These classifications are important in geometry, as they form the basis for many other geometrical concepts and relationships.

Polygons and Circles

A polygon is a closed figure bounded by three or more line segments, with each line segment intersecting only two other line segments. Polygons can be classified based on the number of sides they have. A five-sided polygon is called a pentagon, while an eight-sided polygon is called an octagon. Polygons with more than ten sides are usually referred to by their number of sides, such as a 12-gon or a 15-gon.

Another fundamental geometrical figure is the circle. A circle is defined as a set of all points in a plane that are equidistant from a given point (the center). The circumference of a circle is the distance around its edge, while the diameter is the distance across the center of the circle. The area of a circle is given by the formula A = πr², where r is the radius of the circle.

Measurement and Calculation in Geometry

In geometry, measurement plays a crucial role. We measure the length of line segments, the size of angles, the area of polygons, and the volume of three-dimensional figures. Calculating these measurements is an essential part of geometry, and there are many formulas and techniques that enable us to do so.

For example, to calculate the area of a rectangle, we simply multiply the length by the width. The formula for finding the area of a triangle is 1/2(base x height). The area of a circle is given by the formula A = πr². These formulas are used frequently in geometry to calculate the various measurements of shapes and figures.

Applications of Geometry

Geometry has many practical applications in science, engineering, and technology. For example, architecture and construction rely heavily on geometric principles to design buildings and structures that are both functional and aesthetically appealing. Geometry is also used in computer graphics, where complex three-dimensional shapes are generated through the use of mathematical algorithms.

Another area where geometry is used is in navigation and mapping. By using geometric principles, we can accurately measure distances and angles, enabling us to create detailed maps of the world around us. Geometric principles are also used extensively in physics and astronomy, where they are used to study the behavior of objects in motion, such as the rotation of planets and the orbits of satellites.


Geometry is a fundamental branch of mathematics that is essential in understanding the properties and relationships of shapes, figures, and space. By mastering the basic concepts and terminology of geometry, we can gain a better understanding of the world around us and the many practical applications of this important subject. Whether in architecture, engineering, or science, geometry is a critical tool for solving complex problems and advancing our understanding of the world in which we live.