GKT101: General Knowledge for Teachers – Math

The prefix "quad-" means "four", and "lateral" is derived from the Latin word for "side". So a quadrilateral is a four-sided polygon. Since it is a polygon, you know that it is a two-dimensional figure made up of straight sides. A quadrilateral also has four angles formed by its four sides.

 

$\begin{align*}AB\end{align*}$, $\begin{align*}BC\end{align*}$, $\begin{align*}CD\end{align*}$ and $\begin{align*}DA\end{align*}$ are the sides and $\begin{align*}A\end{align*}$, $\begin{align*}B\end{align*}$, $\begin{align*}C\end{align*}$ and $\begin{align*}D\end{align*}$ are the vertices of the quadrilaterals.

Line segments $\begin{align*}AC\end{align*}$ and $\begin{align*}BD\end{align*}$ joining two non-consecutive vertices are called diagonals.

Two sides like $\begin{align*}AB\end{align*}$ and $\begin{align*}AD\end{align*}$ having a common endpoint are called adjacent sides.

There are many common special quadrilaterals that you should be familiar with. Below, these special quadrilaterals are described with their definitions and some properties.

Source: CK-12, https://flexbooks.ck12.org/cbook/ck-12-interactive-geometry-for-ccss/section/1.5/primary/lesson/quadrilaterals-geo-ccss/

 This work is licensed under CK-12 Curriculum Materials License.