# Online Math Dictionary: D

Easy to understand math definitions for K-Algebra mathematics
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 decagon decameter deceleration decimal degree of an angle degree of  a  polynomial denominator diameter difference digit dihedral  angle distributive property dividend divisor dodecagon dodecahedron

 DecagonA decagon is a ten sided polygon.  The picture on the right is a regular decagon since all the sides and angles are the same (congruent.)   For more info, check out Properties of Decagons.  Decameter
A decameter is 10 meters (in the metric system).   The prefix "deca" mean "ten of."  In U.S. measurement, a decameter is about 32.808 feet. Deceleration
Deceleration is a slowing down of your speed (velocity).  In physics, you just say "acceleration" whether you are speeding up or slowing down...  It just means that the speed is changing.  Decelerating is slowing down. Decimal
Decimal numbers are like fractions because they count PART of something. Whole numbers (0, 1, 2, 3, ...) count whole things  -- like a whole pizza.  You can use a decimal number to count part of the pizza.  Half of a pizza would be 0.5 of a pizza.  One-fourth of a pizza would be 0.25 of a pizza.
Examples:   2.34      45.009       0.3737373