geometry
the branch of math that deals with measurement, properties, and relationships of points, lines, angles, planes and two and three dimensional figures
point
an exact location in space; a point has no length or width
line
an infinite set of points in opposite directions forming a straight path; it has only on dimension: length
line segment
the set of points on a line consisting of two fixed points and all of the points in between
parallel lines
lines in the same plane that never intersect no matter how far they extend; they are always the same distance away from each other
intersecting lines
two lines that share exactly one point
ray
part of a line that has one end point and extends infinitely in the other direction
vertex
(1) the common endpoint of two sides of a polygon(2) the common endpoint of two rays that form an angle(3) the common endpoint where two or more edges of a three dimensional figure meet
side
a line segment joining two adjacent vertices of a polygon(the segment that connects two angles of a polygon)
angle
a geometric figure formed by two rays that have a common endpoint
right angle
an angle that is formed by two perpendicular lines; it measures exactly 90 degrees
perpendicular
line segments or rays that intersect to form right angles
acute angle
angle whose measure is greater than 0 degrees and less than 90 degrees
obtuse angle
an angle whose measure is greater than 90 degrees and less than 180 degrees
straight angle
an angle whose measure is exactly 180 degrees
polygon
a closed, plane figure formed by three or more line segments(the interior angles of a triangle equal 180 degrees)
triangle
a polygon with three sides and three angles
right triangle
a triangle with one right angle
equilateral
having equal sides (An equilateral triangle has all sides equal)
acute triangle
a triangle in which all three angles are acute
isosceles triangle
a triangle with two sides that are equal
scalene triangle
a triangle with no sides equal
obtuse triangle
a triangle with one obtuse angle
quadrilateral
a polygon with 4 sides and 4 angles
parallelogram
a quadrilateral with two PAIRS of parallel sides
square
a rectangle with all 4 sides equal; it has four 90 degree angles
rectangle
a quadrilateral with 4 right angles(the interior angles of a rectangle equal 360 degrees)
trapezoid
a quadrilateral with exactly one pair or parallel sides
rhombus
a parallelogram with 4 equal sides (it does not have 90 degree angles)
pentagon
a polygon with five sides and five angles
hexagon
a polygon with six sides and six angles
heptagon
a polygon with seven sides and seven angles
octagon
a polygon with eight sides and eight angles
nonagon
a polygon with nine sides and nine angles
decagon
a polygon with ten sides and ten angles
corresponding sides
sides in the same relative position on two congruent or similar figures; (the corresponding sides of congruent figures are equal, and the corresponding sides of similar figures are proportional)
congruent
two or more shapes having exactly the same size and shape;(they form a perfect match when one is placed atop the other)
similar figures
figures that have the same shape, but are not necessarily the same size
corresponding angles
angles in the same relative position on two congruent or similar figures; the angles are equal
line of symmetry
a line that divides a figure into two equal halves that are mirror images of each other; a simple test to determine if a figure has a line of symmetry is to fold the figure along the imagined line of symmetry to see if the two sides match Some shapes have more than one line of symmetry!
symmetry
the property of having the same size and shape across a dividing line
formula
a mathematical statement, equation or rule that shows a relationship between two or more amounts
perimeter
the measure of the distance around the outside of a closed figure; P = (2 X L) + (2 X W) or P = s + s + s + s