1st Grade · Geometry
1.G.A.1: Distinguish between defining attributes and non-defining attributes
1.G.A.1 is a 1st grade Common Core math standard in Geometry. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Distinguish between defining attributes (e.g., triangles are closed and three-sided) versus non-defining attributes (e.g., color, orientation, overall size); build and draw shapes to possess defining attributes.
In plain words
Distinguish between defining attributes and non-defining attributes.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
What must be true for a shape to be a triangle?
- It must have 3 straight sides.
- It must be blue.
- It must be big.
Where students can get stuck
- Rejecting a triangle that is upside down or long and thin, because it does not look like the usual pointing-up picture.
- Calling a square tilted on one corner a diamond, and therefore not a square, because it has been turned.
- Accepting a shape with a gap or a curved side as a triangle because it has three corners.
Effective teaching strategies
- Draw triangles that are tall, flat, upside down, and large, and ask what stays the same in all of them, so students name closed and three straight sides.
- Turn a paper square on its corner and ask whether it is still a square, then have students count its sides and check its square corners to find out.
- Show a three-cornered drawing with a gap in one side or a curved side, and ask which defining attribute is missing, so it is not a triangle.
Units that teach this standard
Find where 1.G.A.1 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Everyday Mathematics
Go Math!
i-Ready Classroom Mathematics
Illustrative Mathematics
Into Math
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read What makes a triangle a triangle for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice geometry at home
In Bobby's Math Club, students practice at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free for every family.
See how it works for teachers
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.