Tangent circles (internal): Two circles are internally tangent if they intersect in exactly one point and one circle lies in the interior of the other circle.
Tangent circles (external): Two circles are externally tangent if the meet in exactly one point and neither circle has any points in the interior of the other circle.
Tangent line to a circle: A line that intersects a circle in exactly one point.
Tangent segment: A line segment that is a subset of a tangent line. This usually refers to the line segment drawn from an external point to the point of tangency.
Tangram : A traditional Chinese puzzle made of a square divided into seven pieces (one parallelogram, one square and five triangles) that must be arranged to match particular designs.
Tessellation: A repeating pattern covering a plane.
Tetrahedron : A polyhedron with four faces; one of the five Platonic solids that has four equilateral triangles as faces (pyramid).
Theorem: A general statement that requires proof.
Three-dimensional space: The set of all points in space. The position of each point can be represented by a unique ordered triple (x,y,z).
Thrice : Three times as many.
tonne : A unit of mass equal to 1,000 kilograms.
The abbreviation is t.
Transformation: A one-to-one mapping of points in the plane to points in the plane.
Transformational geometry: A method for studying geometry that illustrates congruence and similarity by the use of transformations.(from math dictionary t)
Transformational proof: A proof that employs the use of transformations.
Transitive property of equality: A property of the real numbers that states: If a = b and b = c then a = c .
Translation: A transformation where every point moves the same direction through the same distance.
Transversal: A line that intersects two (or more) other lines in distinct points.
Trapezoid: A quadrilateral with exactly one pair of parallel sides.
Triangle inequality theorem: In any triangle, the sum of the lengths of two sides is greater than the length of the third side.
Trichotomy property: A property of the real numbers that states: for every x and y, one and only one of the following conditions is true: x < y; x = y, x > y.
Trigonometry of the right triangle: The trigonometric functions for acute angles are the ratios of the sides of the right triangle containing the angle.
Trillion : Usually means a million millions. 1,000,000 x 1,000,000 = 1,000,000,000,000 A 1 followed by 12 zeros, 1 × 1012.
Trinomial : A polynomial with three terms.
Truth value: A value, (typically T or F), indicating whether a statement is true or false.
Twelve-Hour Clock : Is where the time is told using the 12 hours from midnight to midday (the morning or "AM" hours), and the 12 hours from midday to midnight (the "PM" hours, afternoon and night) 8 hours after midnight is written as 8:00 AM 3 hours and 30 minutes after midday is written as 3:30 PM (equal to 15:30 on 24-hour time)
Twenty-Four Hour Clock : Is where the time is told using the full 24 hours in the day.
Two column proof : The outline of a written proof in which the statements and their corresponding reasons are listed in two separate columns.
Two-dimensional space: The set of all points in the plane. The position of each point can be represented by a unique ordered pair (x,y). Figures such as angles, pairs of parallel and intersecting lines, circles and polygons exist in two-dimensional space.(from math dictionary t)