**Quadrilateral-**A **quadrilateral** is a four-sided polygon with four angles.

**Parallelogram-**A **parallelogram** is a quadrilateral with opposite sides parallel (and therefore opposite angles equal).

**Rectangle- **a **rectangle** is a quadrilateral with four right angles. It can also be defined as an equiangular quadrilateral. Square-a plane figure with four equal straight sides and four right angles.

**Rhombus-** is a simple (non-self-intersecting) quadrilateral whose four sides all have the same length. **Trapezoid-**A **trapezoid** is a quadrilateral with two sides parallel. **Trapezium-** used to describe a geometric shape, has two contradictory meanings.

**Acute angle-**The **acute angle** is the small **angle** which is less ,. **Right angle-**, a **right angle** is an **angle **that bisects the **angle** formed by two adjacent parts of a straight line. **Coplanar lines-**are **lines** that lie on the same plane.

**Parallel lines- **are **lines** in a plane which do not meet; that is, two **lines** in a plane that do not intersect or touch each other at any point are said to be **parallel** **Intersecting lines-**This shared point is called the point of intersection. Although we’re dealing specifically with **lines** in this lesson, **line **segments also **intersect** where they share a common point.

**Perpendicular-** is the relationship between two **lines** which meet at a right angle (90 degrees). **Transversal-** is a line that passes through two lines in the same plane at two distinct points.

**Corresponding angles**– the **angles** in matching corners.

**Alternate Interior Angles-**The **pairs of angles** on opposite sides of the transversal but inside the two lines.

**Alternate Exterior Angles-**The **pairs of angles** on opposite sides of the transversal but outside the two lines.

**Same Side Interior Angles**– are two **angles **that are on the **same side** of the transversal and on the **interior** of the two lines.

**Hypotenuse-** is the longest side of a right-angled triangle, the side opposite of the right angle. Zero property- the **zero**-product **property** states that the product of two nonzero elements is nonzero.