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.