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EnchantedLearning.com Math Dictionary

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T is for ...

tally marks Tally marks are a quick way of keeping track of numbers in groups of five. One vertical line is made for each of the first four numbers; the fifth number is represented by a diagonal line across the previous four.

tangent Tangent (abbreviated tan) is a trigonometric ratio, corresponding to the length of the oppsite side divided by the length of the adjacent side of the right triangle.

tangram A tangram is a traditional Chinese puzzle that can be made into many shapes.

tape measure A tape measure is a simple device used to measure things.

temperature Temperature is a measure of the heat. Temperature is measured using a thermometer.

ten Ten is the number between nine and eleven. People have ten fingers and ten toes. Our number system is base 10. A ten-sided polygon is called a decagon.

tetrahedron A tetrahedron is a pyramid formed by four triangles.

thermometer A thermometer is used for measuring the temperature.

third The third person or item comes after the first and second. Third is abbreviated 3rd.

13 ****** ******* thirteen Thirteen is the number after twelve (12) and before fourteen (14). A thirteen-sided polygon is called a tridecagon.

30 ********** ********** ********** thirty Thirty is the number after twenty nine (29) and before thirty one (31). A thirty-sided polygon is called an triacontagon.

1,000 thousand One thousand is a whole number that is equal to 100 times 10.

three Three is the number between two and four. A tricycle has three wheels. A triangle has three sides. A Triceratops is a dinosaur that had three horns. Tri means three!

time Time is measured in seconds, minutes, hours, days, weeks, months, and years.

timeline A timeline is a graphic display that shows a series of events that happen in a time period.

time zone The Earth is divided into 24 time zones so that everyone in the world can be on roughly similar schedules (like having noon when the sun is highest in the sky).

torus A torus is a doughnut-shaped solid object.

transcendental number A transcendental number is a number that is not the root of a polynomial equation with integer coefficients. Examples of transcendental numbers include e and pi .

transversal A transversal is a line that intersects at least two other lines.

trapezoid A trapezoid is a four-sided figure (a quadrilateral) with exactly two parallel sides.

triangle A triangle is a geometric figure (a polygon) that has three sides. The sum of the interior angles of a triangle is 180 degrees. The perimeter of a triangle is the sum of the lengths of the three sides. The area of a triangle is (1/2)base*height. A triangle with three equal sides (and three equal angles) is called an equilateral triangle. A triangle with two equal sides (and two equal angles) is called an isosceles triangle. A triangle with no equal sides (and no equal angles) is called an scalene triangle. A triangle with one right angle is called a right triangle. The Pythagorean theorem states that for a right triangle, the sum of the squares of the two shorter sides is equal to the square of the hypotenuse: a2 + b2 = h2. A triangle with one obtuse angle is called a obtuse triangle. A triangle with all acute angles is called a acute triangle.

2x + 3y trinomial A trinomial is a polynomial expression that has three terms, like 3x2 + 4yz - 5.

trisect To trisect is to divide into three equal parts. For example, if a 90-degree angle is trisected, the result is three 30-degree angles.

12 ****** ****** twelve Twelve (12) is the number between eleven (11) and thirteen (13). Dozen is another word for twelve. A dodecagon is a twelve-sided figure. A dodecahedron is a twelve-sided geometric solid whose faces are pentagons.

twenty Twenty is the number between nineteen and twenty-one. There are twenty (20) apples above. A twenty-sided polygon is called an icosagon.

two Two is the number between one and three. We have two eyes, two ears, two arms, and two legs.

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EnchantedLearning.com Math Dictionary

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Counting

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