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Third Grade Math Vocabulary
Third Grade
Area: The number of nonoverlapping units that cover a closed boundary (measured in square units). 
The area of this square is 9 square units. 
Array: An arrangement of objects in a regular pattern, usually rows and columns. Arrays are commonly used to model multiplication. 
This array has 2 rows and 5 columns. So, 2 × 5 = 10. 
Benchmark Fraction: A fraction which is easily recognizable and can be used to estimate the size of other fractions or to compare other fractions. (ie, ½, ¼, ¾ ) 
2/7is close in size to1/4. 
Capacity: The amount of liquid or dry matter that a container can hold. 
The gas container has a capacity of 5 gallons. 
Common Equivalencies: Units within measurement systems that are equal and can be substituted for each other. (For example, 4 quarts equal 1 gallon, 100 centimeters equal 1 meter, 16 ounces equal 1 pound) 

Commutative Property: A property of addition and multiplication (but not of subtraction and division ) that says that changing the order of the numbers being added or multiplied does not change the answer. 
3 + 6 = 6 + 3 3 − 6 ≠ 6 − 3 8 × 2 = 2 × 8 8 ÷ 2 ≠ 2 ÷ 8 
Conclusion: A sensible decision reached after looking at many facts. 
After looking at the pattern 3, 8, 13, 18, 23,… , the conclusion was made that the next number is 28 based on the observation that 5 was being added each time. 
Congruent Figures: Figures that have exactly the same shape and size. 
Congruent Pentagons These pentagons are the same size and the same shape. One will fit exactly over the other. 
Conjecture: A guess about an outcome before all the facts are known. 
After looking at many examples, students made the
conjecture that order doesn ’t matter when adding, but is important when subtracting. 
Data: Information that is gathered by counting, measuring, asking questions, or observing. A collection of facts from which conclusions may be drawn. 

Decimal: A number that uses place value and a decimal point to show tenths and hundredths. 
The decimal 0.3 is read as threetenths 
Denominator: The number below the bar in a fraction that tells the number of equal parts in the whole. Numerator: The number above the bar in a fraction which represents the number of equal parts being considered. 
In the fraction ¾, the numerator is 3, the denominator is 4. This fraction tells you that you have 3 out of four parts. 
Distributive property: A property that relates multiplication and addition or subtraction. This property gets its name because it “distributes” a factor over terms inside parentheses . 

Division: The process of determining how many equal groups can be made from a quantity. Division is the inverse of multiplication. 
10 divided by 5 equals 2. (How many groups of 5 are in 10? There are two groups of 5.) 
Elapsed time: The amount of time taken to go from a start time to a finish time. 
The soccer game started at 5:30 P.M. The game was
over at 6:15 P.M. The elapsed time was 45 minutes. It took a total of 45 minutes to play the game. 
Equation: A number sentence that contains an equal sign. 
7 + x = 10 and 25 = 29 − ϑ are both equations. 
Equivalent Fractions: Fractions that have different denominators but name the same amount. 

Estimation: An answer that should be close to an exact answer. 
53 + 38 can be estimated as 50 + 40 = 90 
Expanded Form : A numeral showing the sum of values of each digit. Standard Form A numeral shown as the sum of its place value addends is standard form. 
50,000 + 3,000 + 200 + 5 = 53,205 (expanded form) (standard form) 
Factor: Any of the numbers that are multiplied to find a product. 
5×3 = 15 5 and 3 are factors and 15 is the product. 
Frequency Table: Data which shows the amount of times that a number occurs. 

Graph (using different types): A picture representation of data such as bar graphs , line plots , pictographs and frequency tables. 

Justify: To demonstrate that a statement is correct or valid. To give a reason to support an answer. 
Find the next number in the pattern and justify
the answer: 98, 87, 76, 65, … The next number is 54
because you subtract 11 each time to 
Line of Symmetry : A line drawn through a figure that divides the figure into two parts that are mirror images of each other. When you fold a figure along its line of symmetry, both parts match. 

Line Plot: A sketch of data in which check marks, Xs, or other marks above a labeled line show the frequency of each value. 

Measurement: A number used to describe the quantity, dimension, weight, or capacity of an object. 
The measurements of the room were 10 ft by 12 ft,
so the area was 120 square feet. 
Metric system: A measurement system based on the baseten numeration system. 
10 millimeters = 1 centimeter 100 centimeters = 1 meter 1000 milliliters = 1 liter 
Multiple: A number is a multiple of a given number if it is evenly divisible by that number. If you skip count by fours from 0, you name multiples of 4. 
0, 3, 6, 9, and 12 are multiples of 3. 0, 25, 50, 75, and 100 are multiples of 25. 
Number Sentence: A complete numerical statement using mathematical symbols demonstrating an equality or an inequality . 
12 = 9 + 3 and 15 + 30 + 50 < 100 are number sentences. 
Ounce/ Gram: Units used to measure weight. 
Small weights are measured in ounces or
milligrams and heavier weights are measured in pounds or grams. 
Parallel/ Perpendicular/ Intersecting Lines: Parallel lines are always the same distance apart, and never meet or cross. Perpendicular lines meet at right angles. Intersecting lines meet or cross one another. 

Perimeter: The distance around a closed 2dimensional shape. 
The perimeter of the triangle is 12 units. 
Pictograph: A graph that uses pictures or symbols to represent numbers. 

Place value: A system for writing numbers in which the value of a digit depends on its place in the number. 
The 5 in the number 25,692 has a place value of 5 thousand. 
Plane/ Solid Figures: Plane figures are twodimensional shapes such as rectangles, squares and circles . Solids are threedimensional shapes such as prisms, pyramids and spheres. 

Probability (conceptual): The possibility that an event will happen. 
Terms used to describe probability are likely ,
unlikely, certain, possible or impossible. 
Properties: Basic characteristics. 
Three properties of squares are that they have
four sides, are equilateral and have four right angles. 
Survey: A gathering of a sample of data. A method of gathering information by questioning people in a poll. 
Chris took a survey to find the favorite lunch of students in the cafeteria. 
ThreeDimensional: Solid objects that have length, width, and height and take up space. They have surface area and volume. 

TwoDimensional figures: Flat shapes that have only two dimensions, length and width (plane figures). They have area, but do not have volume. 

Unit Fraction: A fraction that has a numerator of one. 
are unit fractions 
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