Concept

# Boundary

## Boundary Point

The boundary point is the point at the edge of a number line inequality.

The boundary point for the strict inequality $x\gt 4$ is $4.$

## Boundary Line

A boundary line is a line that defines the edge of an area. Usually, this refers to the line that splits a plane in half in the graph of a linear inequality.
In the example above, the line $y=x$ is the boundary line of the non-strict inequality $y\leq x.$

## Boundary Curve

A boundary curve is the same as a boundary line in every way except that the word curve can be used to describe inequalities whose boundaries are not linear functions.
In this example, the curve $y=x^2$ is the boundary curve of the strict inequality $y\gt x^2$