The term symmetry is derived from the Latin word symmetria which indicated commensurateness. In geometry, this term continues to refer to the concept of equality. In this case, however, the concept does not refer to the more commonly thought of definition of equality. Instead, symmetry refers to both parts of a shape or figure as having equal or matching points. These matching points will match in shape, size, proportion, and all appearance. In this way, it could be considered that both parts of the shape match. Proportion, in this instance, does not necessarily refer directly to all parts being equal, but rather to the fact that the relationship between objects and the whole have not in any way changed or been changed.

When one is able to divide something, whether a real object or a drawn shape, into two parts which each look identical to the other, a line of symmetry has been found. Symmetry, in this case, refers to the concept of finding an imaginary line upon which if you folded the object, it would look exactly the same on both sides. Keeping in mind that all aspects of the object must remain the same, as described above. Slight variations would create an object which would be considered asymmetrical. While it is not possible to always fold an object along the line, it is the idea or concept of folding an object which can be the key factor in determining a line of symmetry. Lines of symmetry can run in any direction. They do not need to be truly vertical or horizontal. They may be found on an angle or diagonal. Objects can also have multiple lines of symmetry.

The human body itself is an excellent example of symmetry. Drawing an imaginary line straight down the middle of the body, leaves matching identical features on both sides; however, drawing a line at the waist level leaves very different features on both sides. Dividing the human body along this line would lead to the determination that the human body in this way is asymmetrical. In other words, the parts on both sides of the line do not match in shape, size, appearance or proportion. Therefore, there is only one line of symmetry in the human body.