Mrs. Daniel s Geometry Vocab List

Mrs. Daniel s Geometry Vocab List

Geometry Definition: a branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space.

Reflectional Symmetry Definition: All of the points on one side of the line exactly match with all of the points on the other side of the line.

Definition: looks that same after you turn the image around a point by less than 180 degrees. The number of times you can turn the image determines the type of rotational symmetry. Rotational Symmetry

Point Definition: Location only; it has no size. How to Name: One capital letter. Example: P

Line Definition: Straight continuous arrangement of infinitely many points. How to Name: Two capital letters with a line with 2 arrows above it. Example: CD

Plane Definition: Flat surface that extends infinitely along its length and width. How to Name: One capital script (cursive) letter. Example: M

Collinear Definition: On the same line

Coplanar Definition: On the same plane

Ray Definition: A point on a line, and all the points that lie on one side of this point. How to Name: Two capital letters and a line with one arrow above. The endpoint must be the first letter. Example: FR

Line Segment Definition: Part of line. Does not extend indefinitely. How to Name: Two capital letters and a line on top. Example: AB

Midpoint Definition: Point on a line segment that is the same distance from both end points. (must be drawn with tic marks)

Congruent Definition: Equal. The same length. The same size. The same measure. Drawn with tic marks.

Bisects/Bisector Definition- Divides into two equal, congruent parts. Line: divides into two congruent segments Angle: divides into two congruent angles (must be drawn with tic marks)

Angle Definition: Formed by two rays that share a common endpoint. How to Name: One or three letters. Angle symbol ( ) in front. Example: B or ABC

Vertex Definition: Common endpoint of the two rays in an angle

Perpendicular/Perpendicular Bisector Definition: Lines that meet at a 90 degree angle. Symbol: For example: AB CD (must be drawn with right angle mark)

Parallel Definition: Lines that never intersect (cross/touch). Symbol: Example: ST CG

Complementary Angles Definition: 2 angles that add up to 90 degrees.

Supplementary Angles Definition: 2 angles that add up to 180 degrees.

Linear Pair of Angles Definition: Two angles on one line. Sum to 180 degrees.

Right Angle Definition: Angle measure of exactly 90 degrees. Symbol: Drawn with a box

Acute Angle Definition: Angle measure of less than 90 degrees.

Obtuse Angle Definition: Angle measure of more than 90 degrees, but less than 180.

Polygon Definition: A closed figure. How to Name: All capital letters. Use as many letter as sides to the polygon. Some Examples:

Concave Definition: Polygon dips inward (Some diagonals can be drawn outside the shape).

Convex Definition: Polygon only points outward. (No diagonals can be drawn outside the shape).

Regular Polygon Definition: A closed figure, with congruent sides and congruent angles. All sides and angles marked congruent.

Perimeter Definition: Sum of the lengths of the sides. Perimeter = 26cm

Area Definition: The amount of space inside the boundary of a flat (2-dimensional) object such as a triangle or circle.

Right Triangle Definition: A triangle with one 90 degree angle. Marked with box

Acute Triangle Definition: A triangle with three acute angles.

Obtuse Triangle Definition: A triangle with one obtuse angle.

Scalene Triangle Definition: Triangle with no congruent sides. Each side is marked with a different number of hash marks.

Isosceles Triangle Definition: Triangle with at least two congruent sides and two congruent angles. Picture: Marked with two congruent sides and two congruent angles.

Equilateral Triangle Definition: Triangle with three congruent sides and angles. Marked with three congruent sides and three congruent angles.

Quadrilateral Definition: Any closed four-sided figure. Some Examples:

Parallelogram Definition: A quadrilateral with two pairs of parallel sides. Marked parallel and congruent.

Rhombus Definition: Two pairs of parallel sides and 4 congruent sides. Marked parallel and congruent.

Rectangle Definition: Two pairs of parallel sides and 4 congruent angles Marked parallel, congruent and 4 right angles.

Square Definition: 4 congruent sides and 4 congruent angles Marked parallel, congruent and four right angles.

Circle Definition: a set of all points in a plane at a given distance from a given point (center/origin).

Radius/Diameter Definition: The given distance from center/origin of the circle to the edge. Diameter is a chord that passes through the origin/center.

Chord Definition: A line segment whose endpoints lie on the circle. The diameter is the longest chord.

Tangent Definition: A line that touches (intersects) the circle only once. The point the circle touches the circle is named the point of tangency.

Semicircle Definition: Half of a circle.

Cylinder Definition: a solid geometric figure that is composed of two parallel congruent circles (bases) and a rectangle as a lateral face.

Prism Definition: solid geometric figure that has two parallel congruent bases that are connected by lateral faces that are parallelograms

Sphere Definition: a round solid figure, or its surface, with every point on its surface equidistant from its center.

Cone Definition: solid geometric figure that has a flat base (frequently, though not necessarily, a circle) and tapers to a point called the apex or vertex.

Pyramid Definition: solid geometric figure formed by connecting a polygonal base with a point forming triangular lateral faces.