1. Linear function is only the linear ratio of independent variable and dependent variable, and the image in plane coordinate system is generally a straight line.

2. A one-dimensional linear equation is an equation, that is, the independent variable or dependent variable is equal to 0. Usually, its solution is the intersection of a straight line (in a plane coordinate system) with the X axis and the Y axis.

3. One-dimensional linear inequality, independent variables and dependent variables are linked by an inequality symbol. Its solution is generally a region (that is, in the plane coordinate system, its solution is generally that the upper part or the lower part of the image is a straight line).