Geometry Vocabulary

Geometry VocabularyA Third Grade UnitcentimeterA metric unit used to measure length.1 centimeter

Line SegmentA part of a line. A line segment has two endpoints. It starts and stops.

LineA straight path that goes on forever in both directions

HorizontalA line that extends from left to right.

verticalA line that extends up and down.

Parallel linesLines that never intersect or cross.

Perpendicular linesTwo lines that cross or meet to form right angles or square corners.

perimeterThe distance around the outside of a figure. To find perimeter all of the sides in the shape are added together.

side + side + side = perimeter

4 cm4 cm3 cm4 cm + 4 cm + 3 cm = 11 cm

quadrilateralA figure with four sides.

Adjacent sidesTwo sides that meet at a point. They are next to each other.They are NOT opposite each other.abcdSides a and d are adjacent to each other.Sides a and c are opposite each other.

parallelogramA quadrilateral with both pairs of opposite sides parallel. Only one set of opposite lines are parallel.

RectangleA parallelogram that has 4 right angles. Opposite sides are the same length.4 cm4 cm2 cm2 cm

squareA special rectangle with four sides of the same length andfour right angles. 3 cm3 cm3 cm3 cm

rhombusA parallelogram with equal sides. A rhombus does not have to have right angles but it can. 3 cm3 cm3 cm3 cm2 cm2 cm2 cm2 cm4 cm4 cm4 cm4 cm