Decagon - A polygon/shape that has ten angles and ten straight lines.
Decimal - A real number on the base ten standard numbering system.
Denominator - The denominator is the bottom number of a fraction. (Numerator is the top number) The Denominator is the total number of parts.
Degree - The unit of an angle, angles are measured in degrees shown by the degree symbol: °
Diagonal - A line segment that connects two vertices in a polygon.
Diameterl - A chord that passes through the center of a circle. Also the length of a line that cuts the shape in half.
Difference - The difference is what is found when one number is subtracted from another. Finding the difference in a number requires the use of subtraction.
Digit - Digits are making reference to numerals. 176 is a 3 digit number.
Dividend - The numer that is being divided. The number found inside the bracket.
Divisor - The number that is doing the dividing. The number found outside of the division bracket.