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Gravity
This is a list of geometry terms that all 8th graders should be familiar with.
Terms in this set (78)
line
a series of dots so close together that they appear as one continuous thing; there is no beginning or end to a "line".
ray
a part of a line that extends indefinitely from one direction
line segment
two endpoints and the straight path between them; a "line" with a beginning and an ending.
intersecting lines
two or more lines that meet and cross at any angle.
perpendicular lines
lines that intersect at a right angle
parallel lines
lines going in the same direction without touching; two lines (or line segments) with the same slope that are always the same distance apart.
congruent figures
figures that are the same size and shape
vertical
line going up and down
horizontal
lines going side to side
plane
is a flat two-dimensional surface that is unending in all directions
angle
two rays with a common endpoint
right angle
an angle that measures 90 degrees
acute angle
an angle with a measure greater than 0 degrees and less than 90 degrees
obtuse angle
an angle that measures greater than 90 degrees and less than 180 degrees
reflex angle
angle that measures more than 180 degrees and less than 360 degrees
complementary angle
if the sum of two angles measures 90 degrees
supplementary angle
if the sum of two angles measure 180 degrees
straight angle
180 degree angle
transversal
a line that intersects two or more other lines at different points
pi
The value that shows the relationship of a circle's circumference to its diameter; it has an approximate value of 3.14 or the fraction 22/7
polygon
a closed figure with three or more straight sides
circumference
the distance around the edge of a circle
two ways to measure triangles
side length and angle measures
right triangle
a triangle with one right angle
acute triangle
triangle whose interior angles are all acute
obtuse triangle
triangle that has one angle more than 90 degrees
equilateral triangle
a triangle with three congruent sides
isosceles triangle
a triangle with two equal sides, the two base angles are also equal
scalene triangle
all sides are different
measure of the interior angles of a triangle
180 degrees
faces
the flat surfaces of a 3-D figure
edges
the intersection of faces of a 3-D figure
square
a parallelogram with all sides congruent and all angles congruent
rectangle
a quadrilateral with four right angles; opposite sides are parallel and congruent
trapezoid
a quadrilateral having two sides parallel
rhombus
a parallelogram with four equal sides
parallelogram
a quadrilateral that has both pairs of opposite sides parallel
circle
the set of all points in a plane that are the same distance from a given point
radius
the distance from the center of the circle to any given point on the circle
diameter
the distance across the circle through the center
circumference
the distance around a circle
arc
a curved line or segment of a circle
surface area
the sum of the areas of all the faces and bases of a solid figure; measured in square units
area
the number of the square units in a figure
perimeter
the distance around any closed figure
volume
the amount of space a 3-D figure containes; the number of cubic units in a 3-D figure.
quadrilateral
a polygon with four sides
pentagon
a polygon with five sides
hexagon
a polygon with six sides
heptagon
a polygon with seven sides
octagon
a polygon with eight sides
nonagon
a polygon with nine sides
decagon
a polygon with ten sides
solid
a three-dimensional (3-D) figure
base
the bottom side of a geometric figure from which the altitude or height can be constructed
dodecagon
a 12 sided polygon
prism
a 3-D figure that has two parallel and congruent bases in the shape of a polygon and at least three lateral faces shaped like rectangles; has a first name (after base) and last name is prism
pyramid
a solid figure that has a polygon for a base and triangles for sides; has a first name (after base) and last name is pyramid
cone
a 3-D figure with curved surfaces, a circular base, and one vertex
cylinder
a 3-D figure with ll curved surfaces, two circular bases, and no vertex; the net of a cylinder is formed by two circles and one rectangle
net
A two-dimensional pattern that can be folded to make a three-dimensional prism or pyramid
regular figure
a figure in which all sides are equal in length and all angles are of the same measure
equilateral
means that all sides are equal
sum
the answer to an addition problem
difference
the answer to a subtraction problem
product
the answer to a multiplication problem
quotient
the answer to a division problem
sum of the interior angles of a polygon
(n-2)180 ; with n as the number of sides in the figure
sum of the exterior angles of a polygon
ALWAYS 360 degrees
each interior angle of a regular polygon
180 - (exterior angle measure)
each exterior angle of a regular polygon
360 divided by (# of sides)
rhombus
has four equal sides
corresponding angles
angles that lie on the same side of a transversal and in corresponding positions
alternate interior angles
angles that lie within a pair of lines and on opposite sides of a transversal
adjacent angles
angles that share a vertex and a side but have no interior points in common
vertical angles
angles that are opposite from each other; formed from two intersecting lines
lateral area
the sum of the areas of the lateral surfaces (only the sides, no bases) of a 3-D figure
height of a figure
the perpendicular distance from the base to the opposite side of the figure (always forms a right angle with the base); also called the altitude
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