Geometry Flashcards for Grades 3-4 (copy)

These flashcards cover key geometry vocabulary and definitions related to angles, lines, and shapes.

Obtuse Angle

An angle greater than 90 degrees but less than 180 degrees.

Acute Angle

An angle that is less than 90 degrees.

Right Angle

An angle that measures exactly 90 degrees.

Line Segment

A part of a line that has two endpoints.

Ray

A part of a line that starts at one point and goes on forever in the opposite direction.

Perpendicular Lines

Lines that intersect at a right angle.

Parallel Lines

Lines that never touch and are always the same distance apart.

Quadrilateral

A polygon that has four sides.

Rhombus

Four sides of equal length.

Rectangle

Four right angles.

Square

Four equal sides and four right angles.

Parallelogram

2 pair of parallel sides.

Trapezoid

One pair of parallel sides.

Circle

A round shape with that is formed by an angle measuring 360 degrees.

Triangle

A polygon with three sides.

Pentagon

A polygon with five sides.

Right triangle

A type of triangle that has one angle measuring 90 degrees. (1 right, 2 acute)

Obtuse Triangle

A type of triangle that has one angle measuring more than 90 degrees. (1 obtuse, 2 acute)

Acute Triangle

A type of triangle with 3 angles measuring less than 90 degrees. (3 acute)

Scalene Triangle

A triangle with no sides of equal length.

Equilateral Triangle

A triangle with 3 equal sides.

Isosceles Triangle

A triangle with 2 sides of equal length.

Line

A straight figure that goes on forever in both directions.

Protractor

A tool used to measure angles in degrees.

Perimeter

The distance around a shape found by adding all the side lengths. L + L + W + W (fence, around, edges)

Area

The space inside a shape, found by multiplying length and width for rectangles. L x W (cover, tiles, inside)

Hexagon

A polygon with six sides.

Octagon

A polygon with eight sides.

Line symmetry

An imaginary line that divides a shape into two identical halves. (mirror image)