Mathematical Terms Glossary - Second Grade Mathematics

Welcome to the comprehensive Second Grade Mathematics Glossary, your complete alphabetical reference dictionary for mathematical vocabulary. In mathematics, words carry exact, powerful meanings: understanding the precise definition of terms allows you to read problems with clarity, communicate your ideas with authority, and connect mathematical concepts across grades. Each entry in this glossary provides a clear definition written for students, accompanied by helpful examples and structural relationships.

Glossary of Mathematical Terms: A through Z

A

Addend: Any number that is added to another number to form a sum. In the equation 24 + 35 = 59, both 24 and 35 are addends. Addition: The mathematical operation of joining two or more quantities together to find their total combined amount. Analog Clock: A circular clock with numbers 1 through 12 and mechanical rotating hands (an hour hand and a minute hand) used to display time. Angle: The interior corner space or opening formed where two straight sides of a polygon meet at a common vertex point. Array: An orderly arrangement of objects, symbols, or numbers organized into straight horizontal rows and straight vertical columns. Associative Property of Addition: The mathematical rule stating that grouping addends differently in parentheses does not change their sum: (a + b) + c = a + (b + c).

B

Bar Graph: A visual data display that uses rectangular bars of equal width whose heights or lengths represent categorical frequencies on a numbered scale. Base-Ten System: Our universal decimal number system based on grouping by tens, where ten units of any place value bundle to create one unit of the next column to the left.

C

Cent (¢): A unit of money in the United States currency system; exactly 100 cents equal one whole dollar ($1.00). Centimeter (cm): A metric unit of linear length; exactly 100 centimeters equal one whole meter. It is roughly the width of a child's pinky fingernail. Column: A vertical line of items or numbers running straight up and down in an array, table, or place value chart. Commutative Property of Addition: The mathematical rule stating that changing the order of addends does not change their sum: a + b = b + a. Comparison Symbols: Mathematical symbols used to compare two quantities: > (greater than), < (less than), and = (equal to). Cube: A three-dimensional solid figure having exactly 6 identical square flat faces, 12 straight edges, and 8 sharp vertices. Cylinder: A three-dimensional solid figure having 2 flat circular bases connected by a smoothly curved surface.

D

Data: Information, numbers, or facts collected through observations, measurements, surveys, or counting experiments. Decade Number: A multiple of ten ending in zero, such as 10, 20, 30, 40, 50, 60, 70, 80, or 90. Decompose: To break a number or shape apart into smaller, friendlier pieces to make calculations or measurements easier. Difference: The result or answer obtained by subtracting one quantity from another; it measures the distance or gap between two numbers. Digit: Any one of the ten fundamental symbols used to write numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Digital Clock: An electronic clock that displays time purely using numbers and digits separated by a colon, without mechanical hands. Dollar ($): A primary unit of currency in the United States, equal to 100 cents. Doubles Fact: An addition equation where a number is added to itself, such as 6 + 6 = 12 or 8 + 8 = 16; doubles sums are always even numbers.

E

Edge: The straight line segment on a three-dimensional solid where two flat faces intersect. Elapsed Time: The total duration or amount of time that passes between the start of an event and the end of that event. Equal Groups: Separate collections that contain the exact same number of items; the foundation of multiplication and division. Equal To (=): A mathematical relationship indicating that two quantities or expressions have the exact same value. Equation: A formal mathematical statement showing that two expressions are equal, containing numbers, operations, and an equals sign. Even Number: Any whole number that can be split into two equal whole-number teams or paired into partners with zero leftovers; ends in 0, 2, 4, 6, or 8. Expanded Form: A way of writing a number that displays the true numerical value of each digit added together, such as 400 + 50 + 8.

F

Face: A flat two-dimensional polygon surface on a three-dimensional solid figure. Fact Family: A group of four related addition and subtraction equations that use the exact same three numbers (or two equations for doubles). Foot (ft): A standard customary unit of length equal to exactly 12 inches. Fraction: A number that names an equal share or part of a whole shape or set. Frequency Table: An organized table that displays categories alongside tally marks and numerical counts (frequencies).

G

Greater Than (>): A comparison symbol showing that the number on the left has a larger value than the number on the right: 85 > 42.

H

Half / Halves: One of two equal shares that make up one whole shape or quantity; two halves make one whole. Half-Dollar: A United States coin worth exactly 50 cents, or half of a dollar. Hexagon: A closed two-dimensional polygon having exactly 6 straight sides, 6 vertices, and 6 angles. Hour Hand: The shorter, slower hand on an analog clock that points to the hours.

I

Inch (in): A standard customary unit of length roughly equal to the length of a small paperclip; 12 inches make 1 foot. Inverse Operations: Operations that undo each other, such as addition and subtraction.

L

Less Than (<): A comparison symbol showing that the number on the left has a smaller value than the number on the right: 28 < 54. Line Plot: A specialized graph that records measurement data by placing Xs vertically above a horizontal number line.

M

Meter (m): The standard metric unit of length, equal to exactly 100 centimeters; roughly the width of a classroom doorway. Minute Hand: The longer, faster hand on an analog clock that points to the minutes. Minuend: The starting whole number in a subtraction problem from which another amount is subtracted.

N

Number Line: A straight horizontal line marked with numbers at equal intervals, representing continuous numerical distance from zero.

O

Odd Number: Any whole number that has one leftover item when grouped into pairs; ends in 1, 3, 5, 7, or 9. Open Number Line: A blank number line without pre-printed tick marks, used flexibly to record mental math jumps.

P

Partition: To slice or divide a shape or quantity into smaller equal parts or shares. Pentagon: A closed two-dimensional flat polygon having exactly 5 straight sides, 5 vertices, and 5 angles. Picture Graph: A visual data display that uses pictures or symbols to represent counts in each category according to a key.

Q

Quadrilateral: Any closed two-dimensional polygon having exactly 4 straight sides, 4 vertices, and 4 angles. Quarter (Coin): A United States coin worth 25 cents; four quarters make one dollar. Quarter Past: A clock position where 15 minutes have elapsed past the hour; minute hand points to 3. Quarter To: A clock position where 15 minutes remain before the next hour arrives; minute hand points to 9.

R

Rectangular Prism: A 3D solid figure having 6 flat rectangular faces, 12 straight edges, and 8 vertices. Regrouping: The mathematical process of bundling 10 of a smaller place value unit into 1 of the next larger unit, or unbundling 1 larger unit into 10 smaller units. Repeated Addition: Adding the exact same number multiple times; the direct bridge to multiplication: 4 + 4 + 4 = 12. Row: A horizontal line of items or numbers running side to side from left to right.

S

Skip-Counting: Counting forward or backward by a number other than 1, such as counting by 2s, 5s, 10s, 25s, or 100s. Sphere: A perfectly round 3D solid figure with zero flat faces, zero straight edges, and zero vertices. Standard Form: The everyday way of writing numbers using base-ten digits, such as 348. Subtrahend: The quantity being subtracted or taken away from the minuend in a subtraction problem. Sum: The total result obtained by adding two or more addends together.

T

Tally Chart: A data collection chart that records counts using five-stroke tally bundles. Tape Diagram: A visual rectangular bar model used to represent part-part-whole and comparison relationships. Thirds: Three equal shares that combine to form one whole; three thirds make one whole.

U

Unit Interval: The fixed, constant distance between any two consecutive whole numbers on an accurate number line.

V

Vertex (Vertices): The corner point where two straight sides of a 2D shape meet, or where three or more edges of a 3D solid meet.

Y

Yard (yd): A standard customary unit of length equal to 36 inches, or 3 feet. Yardstick: A wooden or metal measuring tool measuring exactly 36 inches (3 feet) long.