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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
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
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
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
The decimal 0.3 is read as three-tenths
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
In the fraction ¾, the numerator is 3,
the denominator is 4. This fraction
tells you that you have 3 out of four
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
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
50,000 + 3,000 + 200 + 5 = 53,205
(expanded form) (standard form)
Factor: Any of the numbers
that are multiplied to find a
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
A picture
representation of data such as
bar graphs , line plots ,
pictographs and frequency
Justify: To demonstrate that a
statement is correct or valid.
To give a reason to support an
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
get the next number.

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 base-ten numeration
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:
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 2-dimensional
The perimeter
of the triangle
is 12 units.
Pictograph: A graph that uses
pictures or symbols to
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 two-dimensional
shapes such as rectangles,
squares and circles . Solids are
three-dimensional shapes such
as prisms, pyramids and
Probability (conceptual):
The possibility that an event
will happen.
Terms used to describe probability are likely , unlikely, certain,
possible or impossible.
Properties: Basic
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
information by
questioning people in a poll.
Chris took a survey to find
the favorite lunch of
students in the cafeteria.
Three-Dimensional: Solid
objects that have length,
width, and height and take up
space. They have surface area
and volume.
Two-Dimensional 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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