Geometry vocabulary

Terms in this set (27)

polygon
A closed figure made up of at least 3 line segments that do not cross, such as a triangle, a quadrilateral, a pentagon, etc.
vertex
A point where two or more straight lines meet.
isosceles triangle
3-sided polygon. 2 congruent sides.
congruent
Having the same size and shape
scalene triangle
A triangle with no congruent sides
equilateral triangle
A triangle with three congruent sides
area of a rectangle
length x width (lw)
perimeter of a polygon
sum of the lengths of the sides
rectangular prism
A solid shape that has: 6 faces (4 rectangles & 2 squares), 8 vertices (corners), and 12 equal edges.
volume of rectangular prism
length x width x depth
midpoint
A point that divides a segment into two congruent segments
line
A straight path that extends without end in opposite directions
reflection
A transformation that "flips" a figure over a mirror or reflection line.
rotation
A transformation in which a figure is turned around a point
radius
A straight line from the center to the circumference of a circle or sphere.
chord
a straight line connecting two points on a circle... can never be longer than the diameter
diameter
A straight line passing from side to side through the center of a circle or sphere.
circumference
The distance around a circle
parallel lines
Lines are parallel if they are always the same distance apart (called "equidistant"), and will never meet.
perpendicular lines
Intersecting at or forming right angles
intersecting lines
lines that cross at one point
similar figures
Figures that have the same shape but not necessarily the same size
line symmetry
a line that divides a figure into 2 halves that match exactly when the figure is folded on that line
acute angle
An angle that is less than 90 degrees
obtuse angle
An angle between 90 and 180 degrees
straight angle
An angle of 180 degrees
reflex angle
An angle greater than 180 degrees (but less than 360)
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