There are three undefined terms in geometry .These words are point, line and plane.Let us look at these :
Point :we define a point as a location that has no length ,width or height.
Line:A line is defined as something that extends infinitely in either direction but has no width and is one dimensional.
Plane : A plane extends infinitely in two dimensions.
The geometric term described as a two-dimensional set of points that has no beginning or end is a line.