Mrs Daniels Geometry Vocab List Geometry Definition a

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. • Picture:

Rotational Symmetry • 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. • Picture:

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

Line •

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

Collinear • Definition: On the same line • Picture:

Coplanar • Definition: On the same plane • Picture:

Ray •

Line Segment •

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

Congruent • Definition: Equal. The same length. The same size. The same measure. • Picture: 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 • Picture: (must be drawn with tic marks)

Angle •

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

Perpendicular/Perpendicular Bisector •

Parallel •

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

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

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

Right Angle • Definition: Angle measure of exactly 90 degrees. • Symbol: Drawn with a “box” • Picture:

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

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

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). • Picture:

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

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

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

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

Right Triangle • Definition: A triangle with one 90 degree angle. • Picture: Marked with “box”

Acute Triangle • Definition: A triangle with three acute angles. • Picture:

Obtuse Triangle • Definition: A triangle with one obtuse angle. • Picture:

Scalene Triangle • Definition: Triangle with no congruent sides. • Picture: 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. • Picture: 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. • Picture: Marked parallel and congruent.

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

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

Square • Definition: 4 congruent sides and 4 congruent angles • Picture: 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). • Picture:

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. • Picture:

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. • Picture:

Semicircle • Definition: Half of a circle. • Picture:

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.