Dear Classifiers,

“How do we know?” is one of the Big Questions humans ask. Classification is one method humans have come up with to describe the nature of things. We decide what things are by putting them in groups with other “like” things. We also know what things are by excluding them from “non-like” things. You’ve been doing this your whole life. I see Elsie Mae do it all the time with her toys and books. In fifth grade we do the exact same thing, only instead of classifying blocks and stuffed animals, we classify ideas.

So far we’ve classified angles as acute, obtuse, right, straight, or reflex, and we’ve classified triangles as equilateral, isosceles, and scalene. Today, we’ll classify polygons based on their properties. A square is really just the idea of a square, and that idea of a square rests on certain properties. A square is a square and not a triangle because of those properties. You look at a square and know it’s a square, but as classifiers and explainers, today you will describe the properties that make it a square.

Sincerely,

Mr. Heimbuck