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Attribute of a shape
A characteristic or property of a geometric figure, such as its sides, angles, vertices, or size.
Defining attributes
Characteristics that determine what a shape is (for example, a triangle having 3 straight sides).
Nondefining attributes
Characteristics that do not determine a shape's identity, such as color, size, or orientation.
Purpose of identifying defining attributes
To understand why a shape belongs to a particular category rather than identifying it only by appearance.
Vertex
A point where two or more line segments or edges meet.
Angle
A figure formed by two rays or line segments that share a common endpoint.
Two-dimensional (2D) shape
A flat shape that has length and width.
Three-dimensional (3D) shape
A solid shape that has length, width, and height.
Regular polygon
A polygon with all sides equal in length and all angles equal.
Irregular polygon
A polygon whose sides or angles are not all equal.
Polygon
A closed, two-dimensional shape made of straight line segments.
Number of sides in a triangle
3 sides.
Number of sides in a quadrilateral
4 sides.
Rectangle
A quadrilateral with 4 right angles and opposite sides equal in length.
Square
A quadrilateral with 4 equal sides and 4 right angles.
Parallelogram
A quadrilateral with 2 pairs of parallel opposite sides.
Rhombus
A quadrilateral with 4 equal sides.
Trapezoid
A quadrilateral with at least 1 pair of parallel sides.
Face (3D shape)
A flat surface on a three-dimensional object.
Edge (3D shape)
A line segment where two faces meet.
Vertex (3D shape)
A corner point where edges meet.
Cube
A three-dimensional shape with 6 square faces.
Rectangular prism
A three-dimensional shape with 6 rectangular faces.
Sphere
A round three-dimensional shape with 1 continuous curved surface and no edges or vertices.
Cone
A three-dimensional shape with 1 circular base and 1 curved surface that comes to a point.
Cylinder
A three-dimensional shape with 2 circular bases and 1 curved surface.
Composite shape
A figure made by combining two or more simpler shapes.
Net of a 3D shape
A flat, two-dimensional arrangement that can be folded to form a three-dimensional shape.
Transformation (geometry)
A movement or change in the position or size of a shape.
Translation (geometry)
Sliding a shape from one position to another without turning or flipping it.
Rotation (geometry)
Turning a shape around a fixed point.
Reflection (geometry)
Flipping a shape over a line to create a mirror image.
Dilation (geometry)
Changing the size of a shape while maintaining its proportions.
One-to-one correspondence
Matching 1 number word to exactly 1 object when counting.
Cardinality
Understanding that the last number counted represents the total number of objects in a group.
Subitizing
Recognizing the number of objects in a small group without counting each one individually.
Perceptual subitizing
Recognizing the number of objects in a group immediately, without using smaller groups.
Conceptual subitizing
Seeing a group as smaller groups and combining them to recognize the total.
Hierarchical inclusion
Understanding that each number includes all the numbers before it (for example, 5 includes 4 and 1).
Conservation of number
Understanding that the quantity of a group stays the same even when the objects are rearranged.
Counting all
Counting every object in a group from 1 to determine the total.
Counting on
Starting with a known quantity and counting forward to find the total.
Counting back
Starting with a number and counting backward to subtract or find how many remain.
Efficiency of counting on compared to counting all
Students do not need to recount the entire group; they begin with a known quantity.
Composing numbers
Combining smaller numbers to make a larger number.
Decomposing numbers
Breaking a number into smaller parts.
Number bonds
Visual models that show how a number can be separated into two or more parts.
Significance of 5 and 10 as anchor numbers
They help students recognize quantities and develop efficient strategies for adding and subtracting.
Role of a five-frame in number sense
Helps students visualize quantities up to 5 and recognize combinations that make 5.
Role of a ten-frame in number sense
Helps students visualize numbers to 10 and understand combinations that make 10.
Ten-frame
A visual model with 2 rows of 5 spaces used to represent numbers up to 10.
"Make a ten" strategy
Combining numbers to create a group of 10, often to make addition easier.
Number line
A visual representation of numbers in order that can show counting, addition, and subtraction.
Open number line usage
Making jumps forward or backward along an unmarked line to represent addition and subtraction strategies.
Hundred chart
A chart displaying numbers from 1 to 100 in rows of 10.
Role of a hundred chart in understanding number patterns
Enables students to identify counting patterns, skip counting, and relationships between numbers.
Place value
The value of a digit based on its position in a number.
Value of the 3 in 345
300, because the 3 is in the hundreds place.
Value of the 4 in 345
40, because the 4 is in the tens place.
Value of the 5 in 345
5, because the 5 is in the ones place.
Base-ten system
Our number system organized around groups of 10.
Number of ones that make one ten
10 ones.
Number of tens that make one hundred
10 tens.
Decomposition of 345 using place value
3 hundreds, 4 tens, and 5 ones.
Expanded form of 345
300+40+5
Regrouping 34 ones
3 tens and 4 ones.
Concrete mathematical representation
Using physical objects or manipulatives to represent mathematical ideas.
Pictorial mathematical representation
Using drawings, pictures, or diagrams to represent mathematical ideas.
Abstract mathematical representation
Using numbers, symbols, and equations to represent mathematical ideas.
Concrete-representational-abstract (CRA) approach
Teaching a concept through hands-on objects, then drawings, and finally numbers and symbols.
Purpose of multiple mathematical representations
Helps students develop a deeper understanding by seeing the same mathematical idea in different ways.
Manipulatives
Physical objects students use to explore and represent mathematical concepts.
Base-ten blocks
Manipulatives representing ones, tens, hundreds, and thousands.
Unit cube (base-ten blocks)
Represents 1.
Rod (base-ten blocks)
Represents 10.
Flat (base-ten blocks)
Represents 100.
Array
An arrangement of objects in equal rows and columns.
Role of an array in number understanding
Helps students visualize equal groups, repeated addition, and multiplication.
Equivalent representation
Different models or expressions that represent the same mathematical value.
Importance of students explaining their strategies
Helps teachers understand students' mathematical thinking and identify misunderstandings.
Number talk
A short classroom discussion in which students mentally solve a problem and explain their strategies.
Teacher's role during a number talk
Encourage different strategies, ask students to explain their reasoning, and compare approaches.
Open-ended mathematical question
A question that allows multiple strategies or possible answers.
Purpose of asking students how they got an answer
To understand their reasoning rather than focusing only on whether the answer is correct.
Error analysis
Examining a student's incorrect answer or strategy to identify the misunderstanding.
Teacher action when a student makes a mathematical error
Ask questions to uncover the student's thinking and provide support that addresses the misunderstanding.
Formative assessment
Assessment during instruction that helps teachers monitor learning and adjust teaching.
Diagnostic assessment
An assessment used to identify a student's strengths, weaknesses, and specific learning needs.
Observation assessment
Watching and listening to students as they work to gather information about their mathematical understanding.
Rationale for multiple assessment methods
Provides a more complete picture of student understanding.
Eliciting mathematical thinking
Asking questions or providing tasks that reveal how students understand and approach a problem.
Interpreting mathematical thinking
Analyzing a student's explanation, strategy, or work to understand their reasoning.
Supporting mathematical thinking
Providing guidance, questions, and representations that help students develop understanding.
Extending mathematical thinking
Challenging students to build on what they already understand and explore more complex ideas.
Productive mathematical question
A question that encourages students to explain, reason, compare, or justify their thinking.
Reason to avoid immediately telling the correct answer
Students need opportunities to reason, discover relationships, and develop their own understanding.
Regrouping in base-ten mathematics
Exchanging units of one place value for an equivalent amount in another place, such as 10 ones for 1 ten.
Different ways to represent 24
2 tens and 4 ones; 1 ten and 14 ones; or 24 individual ones.
Purpose of trading with base-ten blocks
To help students understand that different groups of units can represent the same quantity.