## Geometry: The study of shapes and their properties

Below are some terms that we learned during our geometry unit in math.

**Angles**: 2 rays joined by a vertex

**Acute**: 0-89 degrees (less than 90)

**Right**: exactly 90 degrees

**Obtuse**: 91-179 degrees (greater than 90, less than 180)

**Straight**: exactly 180 degrees (a line or line segment)

**Polygons**: Closed figures made up of line segments

**Regular**Polygons: All the angles have the same degrees; all the

sides are the same length

**Irregular**Polygons: The sides and angles have different

measurements

**Triangles**: Polygons with 3 sides and 3 angles; Triangles can be classified using 2 names: 1 to describe the lengths of the sides and 1 to describe the angles inside

**Sides**:

**Equilateral**: All sides are the same length

**Isosceles**: 2 of the sides have the same length

**Scalene**: Each side has a different length (no sides the same)

**Angles**:

**Right**: Has one 90 degree angle

**Acute**: All 3 angles are acute (all less than 90 degrees)

**Obtuse**: 1 angle is obtuse (between 90 and 180 degrees)

## Examples of triangles:

**Quadrilaterals**: Polygons with 4 sides and 4 angles; more specific names are given based on the number of parallel sides, the number of sides of equal length, and the measurements of the angles. Some shapes can be classified by multiple names: a square is a type of rectangle, a rhombus is a type of parallelogram, etc.