- The terms multiplicand and multiplier
For those of you who don’t remember or were never taught these terms, multiplicand refers to the first number in a line of multiplication and the multiplier is the second. i.e. in 2×3=6, 2 is the multiplicand and 3 is the multiplier. These terms are useless since multiplication is commutative, and, therefore, it doesn’t matter which number is first. Also, once you are past the 3rd or 4th grade you will never hear these terms again anyway. - Plasma as a fourth state of matter
I know plasma is a fourth state of matter (Bose-Einstein condensate and fermionic condensate are a fifth and sixth according to Wikipedia), but for some reason it was only mentioned in an elementary science class and never again, and I think it’s because no one really understands it. When I took chemistry and materials science in college we did phase change diagrams without even mentioning plasma as a fourth option, just solid, liquid, and gas. If I didn’t need to know it at that level then I definitely didn’t need to learn about it as a 5th grader. - I before E except after C
This just simply gets you in a lot of trouble since there are so many exceptions.