# Online Math Dictionary: D

**Easy to understand math definitions for K-Algebra mathematicsJust scroll down or click on the word you want and I'll scroll down for you! **

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. |

**DecameterA 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.

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.

**DecimalDecimal 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
For more info on decimals, check out my decimal lessons.**