Glossary - Dd

Data

Information collected and used to analyze a particular concept or situation.

Day

A unit used to measure time; 1 day = 24 hours.

Decagon

A decagon is a ten-sided shape (polygon).

Deciles

The 10th, 20th, 30th, ...90th percentile points (See definition for Percentile.)

Decimal Fraction

A fraction using a decimal point to represent the denominator of 10 or a power of 10.

Decimal Number

A fractional number that is written using base ten notation. A mixed decimal number has a whole number part as well. Example: 0.28 is a decimal number and 3.9 is a mixed decimal number.

Decimal Point

A period or dot separating the ones place from the tenths place in decimal numbers or dollars from cents in money. It looks like a period. Example: For "2.13" the decimal point is after the two.

Decimetre

One-tenth of a meter, a decimeter is approximately the distance from one’s wrist to the end of one’s thumb.

Decompose

To break a number into smaller units to simplify computation. Example: 15 = 10 + 5.

Decomposition

The process of breaking a number into smaller units to simplify computation.

Decrease

To take away or become smaller.

Deductive Reasoning

Using logic to arrive at a conclusion from a given premise.

Degree

A unit used to measure angles. There are 360 degrees in a circle.

Degree of a Monomial

The sum of the exponents on the variables contained in a term. Example: The degree of 3x³y⁴ is 7.

Degree of a Polynomial

The largest degree among all its terms.

Denominator

The bottom number of a fraction. For 1/2 the denominator is 2.

Density

The amount of mass per unit of volume.

Dependent Events

Two events in which the outcome of the first event affects the outcome of the second event (e.g., drawing two marbles from a bag of red, green, and blue marbles without replacement).

Diameter

The distance from one side of the circle to the other side when the line (chord) is drawn through the centre point. It is a value that is two times the length of the radius.

Difference

The answer in a subtraction problem. One value is subtracted form another and the result is the difference. Technically, the subtrahend is subtracted from the minuend.

Digit

Any one of the ten numerical symbols:0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Dilation

A transformation that stretches or shrinks a function or graph both horizontally and vertically by the same scale factor.

Dime

A coin with a value of 10 cents or one tenth of a dollar.

Dimensional Analysis

A method of manipulating unit measures algebraically to determine the proper units for a quantity computed algebraically. For example, velocity has units of the form length over time (e.g., metres per second [ m/sec ]), and acceleration has units of velocity over time; so it follows that acceleration has units ( m/sec)/sec = m/(sec²).

Dimensions

Measurements of a figure. Examples include the length, width, and height of a prism.

Direct Measurement

A process of obtaining the measurement of some entity by reading a measuring tool, such as a ruler for length, a scale for weight, or a protractor for angle size.

Discount

A reduction made from the gross amount or value of something; a reduction made from the regular or list price.

Discover

To make note of possible patterns and generalizations that result from investigation/exploration.

Dispersion

The scattering of the values of a frequency distribution (of data) from an average.

Distance

The length of the line segment joining two points.

Distributive Property

A property of real numbers that states that the product of the sum or difference of two numbers is the same as the sum or difference of their products. Example: 6x(2+3)=(6x2)+(6x3) -- Multiplication over addition. Example 2: 5 x 23 = 5 x (20 + 3) = 5 x 20 + 5 x 3 = 100 + 15 = 115.

Dividend

A number that is divided by another number.

Divisible

If a number has a whole number answer when divided by a second number, the first number is divisible by the second number; x is divisible by y if and only if x = qy where y is a whole number.

Division

A mathematical operation involving two numbers that tells how many groups there are or how many are in each group. The symbol for division is ÷ or /.

Divisor

The number by which the dividend is divided.

Dollar

Currency that is worth 100 cents. You will see the symbol "$" when working with dollars.

Domain

The set of values for which a function is defined.

Double

To make twice as great or as many; to increase by adding an equal amount; to amount to twice the number.

Double-Bar Graph

A graph that uses pairs of bars to compare and show the relationship between data.

Double-Line Graph

A graph that uses pairs of lines that show change over time to represent and compare data