D
data
A collection of facts or information.
pages 17–22, 42–43, 44–51, 217–218, 231–233, 252, 338, 343, 346, 351–356, 366–367, 380–383, 384–387, 433–437, 438–441, 520–523, 526–527, 554–555, 560–581
decimal
A number written using the base-ten place value system and containing a decimal point. (See also decimal fraction.)
pages 362–367, 368–374, 375–379, 388–389, 390–395, 396–399, 400–410, 411–419
decimal fraction
A fraction written as a decimal. For example, 0.75 and 0.4 are decimal fractions and 
and 
are called common fractions. (See also common fraction and decimal.)
pages 363–365, 368–374, 386, 579
denominator
The number below the line in a fraction. The denominator indicates the number of equal parts into which the unit whole is divided. For example, 4 is the denominator of the fraction 
. (See also numerator.)
page 58–63, 64–68, 70, 84–85, 94, 98, 105, 111, 389, 458–459, 460–465, 470, 472–473, 475, 477, 504, 515
density
The ratio of an object's mass to its volume.
D = 
pages 539, 543–550
diameter
A line segment that connects two points on a circle and passes through the center.
The length of this line segment.
pages 150, 162, 164–165, 551–559
difference
The answer to a subtraction problem.
pages 160–165, 458–459
digit
The whole numbers from 0 to 9.
pages 121–124, 157, 160–161, 172–176, 177–180, 200, 315, 373–374, 375–376, 405, 407
divide
To separate into equal parts or groups to make "fair shares."
pages 56–57, 294–297, 298–305, 306–314, 315–319
dividend
The number that is divided in a division problem; e.g., 12 is the dividend in 12 ÷ 3 = 4.
page 306
dividing with columns
A division method. (See also column method.)
pages 299–300
division
The operation of making equal groups. For example, there are 3 groups of 5 in 15.
pages 56–57, 294–297, 298–305, 306–314, 315–319
divisor
In a division problem, the number by which another number is divided. In the problem 12 ÷ 4 = 3, the 4 is the divisor, the 12 is the dividend, and the 3 is the quotient.
pages 56, 306
dodecagon
A twelve-sided, twelve-angled polygon.
dozen
A group of 12 people or things.
pages 224, 229, 492–494