Geometry Vocab Words


points lying in the same straight line


an instrument with two arms, one sharp and one with a pencil that can be used to draw circles

Congruent Segment

segments that have the same length


lines/points in the same plane


a straight line joining two opposite corners of a square


lines/points the same distance from each other


a whole number

Intersection of a Line

two or more lines crossing each other

Intersection of a Plane

planes that cross through each other


a straight one dimensional figure that extends in both directions

Line Segment

a pat of a line that has a specific length


consisting of lines


a number's difference from zero

Metric System

the measuring system based on the meter, liter, and gram as units of length, capacity, and weight or mass


the halfway point; the middle of

Natural Number

whole numbers and zero


not occupying the same surface or linear plane

Number Line

a line which numbers are marked at intervals

Perfect Square

the product of a rational number multiplied by itself

Plane (Geometric)

a surface comprising all the straight lines that join any two points lying on it


an exact position or location on a plane surface

Point of Origin

(0,0); where the x-axis and the y-axis intercept


an instrument used in measuring or drawing angles

Rational Numbers

can be made by dividing an integer by an integer


a half-infinite line


a tool used to measure straight lines and measure distances


part of a line or curve

Square Root

a number multiplied by itself


the amount a value can change and still acceptable

U.S. Standard System

units of measurement commonly used in USA


an object that has both a magnitude and a direction


the highest point

Acute Angles

angles that measure less than 90 degrees

Alternate Angles

a pair of angles with different vertices and on opposite sides of a transversal at its intersection with two other lines


the amount of turn between two lines around their common point

Angle Bisector

a line that splits an angle into two equal angles

Complementary Angle

two angles that add up to 90 degrees


curved inwards

Congruent Angle

two or more angles that are identical to each other

Congruent Segments

segments that have the same length


a measure for angles


a mapping of a space onto another or onto itself so the distance between any two points in the original space is the same as the distance between their images in the second space

Linear Pairs of Angles

when two lines intersect each other at a single point

Obtuse Angles

an angle that is more then 90 degrees but less than 180 degrees

Opposite Rays

rays that have the same starting point and extend in opposite directions

Parallel Lines

lines on a plane that never meet

Perpendicular Segment Bisector

a line that intersects another line segment perpendicularly and divides it into two parts of equal measurement

Perpendicular Lines

two lines that intersect each other at right angles

Perpendicular Planes

two planes are at right angles

Right Angles

the angle bounded by two lines perpendicular to each other (90 degrees)

Reflex Angles

an angle that is more than 180 degrees and less than 360 degrees

Supplementary Angles

two angles whose sun equal 180


when two or more parts are identical after a flip, slide or turn


a line that crosses at least two other lines

Vertical Angles

the angles opposite each other when two lines cross; they are always equal