Because we can't really define what a line is. You try defining what a line is and see where you will get: nowhere. That's because a line is so basic that you can't break it down any further to describe it, so we just assume that it is what it is.
There are typically three words in geometry that are undefined. The first is "point." A point has no dimension, length, width, or thickness. The second is "line." A line has no thickness and goes on indefinitely in both directions. The third undefined term is "plane." A plane has no thickness and has no boundaries.
a plane
It is a very basic concept which cannot be defined. Undefined terms are used to define other concepts. In Euclidean geometry, for example, point, line and plane are not defined.
A slope is 0 if it is a straight horizontal line. A slope is undefined if it is a straight vertical line.
Point is not an undefined term. It can be defined as a mathematically precise location, or as the place where two lines intersect.
A ray is not an undefined term.
Line
point , line and plane
In Euclidean geometry point, line and plane are not defined.
There are typically three words in geometry that are undefined. The first is "point." A point has no dimension, length, width, or thickness. The second is "line." A line has no thickness and goes on indefinitely in both directions. The third undefined term is "plane." A plane has no thickness and has no boundaries.
A vertical line has an undefined slope.
a plane
A line is undefined because all points on the line have the same x-coordinate.
A point is an undefined term. But given two points, they can be joined using a line segment.
The term 'undefined' means not precisely limited, determined, or distinguished not precisely limited, determined, or distinguished; "an undefined term"; "undefined authority"; "some undefinenot precisely limited, determined, or distinguished; "an undefined term"; "undefined authority"; "some undefine
No, the slope of a horizontal line is 0. The slope of a vertical line is undefined.
The equation is the definition of the line.If the line is undefined, then it has no equation.