When studying the curl, one often finds the explanation that the curl is a measure of the tendency of a vector field to circulate around a given point. But this doesn't make much sense to me, since there's no clear way to measure "tendency"? What are the units of "tendency"? Wouldn't you agree that it is way more clear and precise to state that the curl is proportional to the tendency of the field to circulate around a given point? I know this is a rather unimportant topic, but I'd like to hear your opinion. Thank you!