Geometry books to help?

[ExcitedMama]

My son is having a lot of trouble understanding geometry basics like angles, line segments and larger shapes. He can’t keep track of a hexagon vs. pentagon and so on. Same issue with understanding polygons and quadrilaterals. I’ve tried going slow and going over the material again and showing him videos but it is not sticking. We do MiF and he’s ahead in all areas of math on his testing with the state and our charter but Geometry is the only one that shows him as a rising 4th grader so it’s definitely a problem area for him. Any books that might help me explain it to him so it clicks?

[kbutton]

My son did state testing in 4th for a different reason, and geometry came up low for him too, but he does okay with geometry while being advanced otherwise. The next year, geometry was not low. All I did was help him learn to classify the different shapes by their terminology. In my son's case, I am guessing he wasn't familiar with the terminology at a memorized level, and that the test was language intense (dyslexic with low working memory). 

Teachers Pay Teachers has some units on this topic. 

Can you change all the shapes to have the same terminology and then show him that he really only needs to know the prefixes? The terminology switches back and forth between using -angle or -lateral or -gon to describe the shapes. Angle after the number of angles, -lateral after the number of sides, and -gon after angles again (different language). I think Tom Clark (Videotext) has a talk on this that he gives at homeschool conventions.

Then quadrilaterals have a classification on whether they are parallelograms, squared in the corners, a trapezoid, etc. There are some good graphic organizers to show that (nested categories). https://www.teacherspayteachers.com/Product/Classifying-Quadrilaterals-In-a-Hierarchy-TEKS-55a-2985343