I find that the ability to remember names of things is not a forte of mine. I’m reading an article from Mathematics Teacher on The Circle Approach to Trigonometry and got to a section where they kept using the word ‘subtended’ and for the life of me I was not picking up what that meant in context (“an angle measure of 1 radian implies that the angle is subtended by an arc 1/(2pi) of a circle’s circumference.”) and I couldn’t pull up a definition from the ol’ memory banks. My brain is a bit slow after a day of reading all the things, so thank goodness for wikipedia and it’s graphics.
The other fun term in this article I think I’ve seen before but never really dug into was covariational relationships. Google search popped up a study from 2002 that defines covariational reasoning as “the cognitive activities involved in coordinating two varying quantities while attending to the ways in which they change in relation to each other.” (p354, Carson, M., et al, Applying Covariational Reasoning, Journal for Research in Mathematics Education, 2002). I like this term a lot as I think it describes the type of reasoning that is very challenging for mathematics students as they are confronted with more and more types of functions.