Download Definition of Geometry Terms

K-­‐5 Geometry Vocabulary This list is meant to be a resource for parents and families to use while supporting their children in mathematics. It represents some of the geometry terms that students need to master, as well as the grade level at which it is introduced. In future grades students will be expected to draw on their understanding of these terms. Term Definition Grade Level Circle A set of points equidistant from a center point K Cube A 3-­‐D prism whose faces are squares K Cylinder A solid shape with two circular bases and a curved K surface. Hexagon A plane shape with six straight sides and six vertices. K Rectangle A quadrilateral with two sets of parallel sides and all K angles congruent. Rhombus A quadrilateral with two sets of parallel sides and all sides K congruent. Square A quadrilateral with all sides congruent and all angles K congruent Triangle A plane shape with three straight sides and three K vertices. Trapezoid A quadrilateral with exactly one set of parallel sides 1 Pentagon A plane shape with five straight sides and five vertices. 2 Area The measure, in square units, of the inside region of a 3 closed two-­‐dimensional figure (e.g., a rectangle with sides of 3 units by 9 units has an area of 27 square units). Array An arrangement of objects in equal rows. 3 Perimeter The distance around a polygon. 3 Polygon A closed-­‐plane figure, having at least three sides that are 3 line segments and are connected at their end-­‐points. Quadrilateral A polygon with 4 sides 3 Acute Angle An angle measuring between 0 and 90 degrees. 4 Angle Two rays with the same endpoint; angles are measured in 4 degrees. Intersect Two lines which cross 4 Line A collection of an infinite number of points in a straight 4 pathway with unlimited length and having no width. Obtuse Angle An angle with a measure of more than 90º but less than 4 180º Ray A portion of a line that begins at an endpoint and goes on 4 indefinitely in one direction. Right angle An angle whose measure is exactly 90º. 4 Right Triangle A triangle with one right angle. 4 Straight Angle Volume Base Line Segment Parallel lines Perpendicular Rectangular Prism Symmetrical An angle that measures exactly 180º. The amount of space occupied in three dimensions and expressed in cubic units. Both capacity and volume are used to measure empty spaces; however, capacity usually refers to fluids, whereas volume usually refers to solids. The line or plane of a geometric figure, from which an altitude can be constructed, upon which a figure is thought to rest. A portion of a line that consists of a defined beginning and endpoint andall the points in between. Two lines in the same plane that are a constant distance apart. Parallel lines never meet and have equal slopes. Two lines, two line segments, or two planes that cross to form a right angle. A 3-­‐D shape whose faces are rectangles. A term describing the result of a line drawn through the center of a figure such that the two halves of the figure are reflections of each other across the line. Updated to align with the Common Core State Standards, 3/11/15. 4 4 5 5 5 5 5 5