Geometry Vocabulary Practice

diameter

chord that passes through the center of the circle

parallel lines

2 lines are parallel if they are coplanar and do not intersect

concentric circles

2 or more circles in the same plane with the same center

congruent triangles

2 triangles are congruent if corresponding sides are congruent and corresponding angles are congruent

rotation

A circular movement. Rotation has a central point that stays fixed and everything else moves around that point in a circle.

rotational symmetry

A figure has rotational symmetry (also called radial symmetry if the figure can be mapped onto itself by a rotation between 0 and 360 degrees about its center of rotation.

geometry

A major branch of mathematics that deals with shapes, sizes, and other properties of figures.

midpoint of a segment

A point that divides the segment into two congruent segments.

transformation

A transformation is an operation that moves, flips, or changes a figure to create a new figure. A rigid transformation is a transformation that preserves size and shape. The rigid transformations are: translations (discussed here), reflections, and rotations. The new figure created by a transformation is called the image . The original figure is called the preimage .

translation

A translation is a transformation that moves every point in a figure the same distance in the same direction. In the coordinate plane, we say that a translation moves a figure x units and y units. Another way to write a translation rule is to use vectors. A vector is a quantity that has direction and size.

angle of rotation

Angle of rotation is the measure of degrees that a figure is rotated about a fixed point.A rotation is a transformation that turns a figure about a fixed point called the center of rotation. Formula 360/n=angle of rotation-n, number of sides on the regular polygon.

right angle

Angle whose measure is 90 degrees

acute angle

Angle whose measure is between 0 degrees and 90 degrees

center of rotation

Center of Rotation is the fixed point around which a 2-dimensional figure is rotated. A 2-dimensional figure always rotates around a point and a 3-dimensional figure rotates around an axis.

point

Has no size, length, width, or height. It is represented by a dot and named by a capital letter

perpendicular bisector

If point A' is the mirror image of point A in a figure with a line of symmetry, then the line of symmetry is the perpendicular bisector of the segment AA'.

apex

In geometry, an apex (Latin for 'summit, peak, tip, top, extreme end;'[1]) is the vertex which is in some sense the highest of the figure to which it belongs.

bisector of a segment

Line, ray segment, or plane that divides a segment into two congruent segments.

segment

Part of a line that consists of two points called endpoints and all points between them.

ray

Part of a line that contains an endpoint and all points extending in the other direction.

non-collinear points

Points that do not lie on the same line

collinear points

Points that lie on the same line

coplanar points

Points that lie on the same plane

probability

Probability of random event-number of events/total possible outcomes

congruent segments

Segments that have the same length

plane

Set of points that has infinite length and width but no height. We name a plane with a capital letter.

angle of elevation

The angle above horizontal that an observer must look to see an object that is higher than the observer.

angle of depression

The angle below horizontal that an observer must look to see an object that is lower than the observer.

hypotenuse

The side opposite the right angle in a right-angled triangle

dilation

To resize something. In general English: to make larger. In Mathematics: to make either larger or smaller.

similar

Two shapes are Similar when the only difference is size (and possibly the need to move, turn or flip one around).

hypothesis

a conditional statement the statement that immediately follows the word if

conditional statement

a statement that can be written in an if-then form

vector

a vector has magnitude (how long it is) and direction

square

all sides congruent and all 4 right angles

straight angle

angle whose measure is 180 degrees

obtuse angle

angle whose measure is greater than 90 degrees but less than 180 degrees

inscribed angles

angle whose vertex is on the circle and whose sides are chords of the circle

center angle of circle

angle whose vertex is the center of the circle and whose rays are radii of the circle

congruent angles

angles that have the same measure

semi circle

arc whose endpoints are the endpoints of a diameter

major arc

arc whose measure is greater than a semi-circle or 180 degrees

minor arc

arc whose measure is less than a semi-circle or 180 degrees

congruent arcs

arcs with equal measure in the same circle or in congruent circles

skew lines

are non-coplaner lines they will not intersect

equidistant

at equal distances

congruent circles

circles that have congruent radii

ratio

comparison of 2 numbers by division

bases

congruent polygons lying in parallel planes

arc

consists of two points and the continuous part of a circle between them

line of symmetry

divides a figure into 2 congruent halves which reflect each other

congruence

equal in size and shape congruent sides/segments have exact same length congruent angles have the exact measure For any set of congruent geometric figures, corresponding sides/angles/faces are congruent.

proportion

equation that states 2 ratios are equal

lateral faces

faces of a prism that are not its bases

function notation

function notation is a system of symbols used in mathematics

transformation

geometric transformations involve taking a preimage and transforming it in some way to produce an image

cone

has a vertex and a circular base

cylinder

has two congruent circular bases in parallel planes

congruent

identical in form coinciding when superimposed

Pythagorean Theorem

in a right triangle, the sum of the squares of the legs is equal to the square of the hypotenuse

cube

is a prism where all sides are squares

oblique prism

is a prism whose lateral faces are parallelograms

right prism

is a prism whose lateral faces are rectangles

triangular prism

is a prism whose parallel faces (the bases)are congruent triangles

perimeter

is the distance around the polygon

area

is the number of square units required to cover the surface

tangent

line in the plane of the circle that intersects the circle at 1 point

secant

line that intersects a circle at 2 points

volume

number of cubic units contained in a solid

rectangle

parallelogram with a right angle

rhombus

parallelogram with consecutive sides congruent

regular polygon

polygon which is both equilateral and equiangular

parallelogram

quadrilateral with both pairs of opposite sides parallel

trapezoid

quadrilateral with exactly 1 pair of opposite sides parallel

angle bisector

ray that divides an angle into two congruent adjacent angles

altitude of a triangle

segment from the vertex of a triangle perpendicular to the line containing the opposite side

median of a triangle

segment from the vertex of a triangle to the midpoint of the opposite side

altitude

segment joining the two base planes and perpendicular to both

chord

segment that connects two points on the circle

radius

segment whose endpoints are the center of the circle and a point on the circle

sphere

set of points in space a given distance from a given point called the center

surface area

sum of the area of all its faces

lateral area

sum of the area of its lateral faces

circumference

the distance around a circle

triangle

the figure formed by three segments joining 3 non-collinear points. Each of the three points is a vertex of the triangle and the segments are the sides.

vertical angles

the non-adjacent angles formed by two intersecting lines

circle

the set of points in a plane that are equidistant from a fixed point called the center

converse

the statement formed by exchanging the hypothesis and the conclusion of a conditional statement

acute triangle

triangle that has all acute angles

right triangle

triangle with a right angle

equiangular triangle

triangle with all angles congruent

equilateral triangle

triangle with all sides congruent

obtuse triangle

triangle with an obtuse angle

isosceles triangle

triangle with at least two sides congruent

scalene triangle

triangle with no sides congruent

supplementary angles

two angles whose sum is 180 degrees

complementary angles

two angles whose sum is 90 degrees

adjacent angles

two coplanar angles with a common vertex and common side between them

perpendicular lines

two lines that intersect to form right angles

polygon

union of 3 or more coplanar segments that meet only at endpoints such that at most 2 segments meet at 1 endpoint and each segment meets exactly 2 other segments.