Strict

An inequality involving the comparison of two quantities that are strictly not equal is called a strict inequality. There are two main kinds of strict inequalities: $$\begin{array}{rl}\text{is less than: }& <\\ \text{is greater than: }& >\end{array}$$ The boundary values in strict inequalities are not included in the solution set. To indicate this graphically, an open point $(\circ )$ is used on number line inequalities and a dashed boundary curve is used on two-dimensional inequalities.

Non-Strict

On the other hand, an inequality that compares two quantities that are not necessarily equal is called a non-strict inequality. There are two main kinds of non-strict inequalities: $$\begin{array}{rl}\text{is less than or equal to: }& \le \\ \text{is greater than or equal to: }& \ge \end{array}$$ The boundary values in non-strict inequalities are included in the solution set. To indicate this graphically, a closed point $(\bullet )$ is used on number line inequalities and a solid boundary curve is used on two-dimensional inequalities.