In Reply to: Unknown entity/quantity posted by Victoria S Dennis on October 13, 2008 at 17:22:
: : Hi,
: : Firstly, what an amazing website! Congratulations.
: : I would like to know where the saying "an unknown entity/quantity" comes from. What is the original saying? I have always believed it to be "entity", but most people use "quantity" now.
: It's "quantity"; it's a metaphor from mathematics. When working out a sum or an equation, the variables whose value you know are "known quantities". Any whose value you don't know, and have to refer to as "X" or "Y", are "unknown quantities".
Victoria is right, as far as standard phrases go; but that still leaves the possibility of legitimate palrticular use of either phrase. "An unknown entity lurked under the bed, or so I thought as a child." That's one way to use "unknown entity," in which an entity is a being, a thing, anything that can be characterized as being something or someone but often can't or needn't be specifically characterized further. You can also use "an unknown quantity" in ordinary language. "My wife seems to have bought an unknown quantity of apples. All I know is that they cost $2.59."