Instead of talking about objects in the real world, mathematicians are mostly interested in talking about objects in the mathematical world- objects like circles, lines, points and numbers.
So, instead of talking about an unknown fish and giving it the variable name "the fish that got away" mathematicians will talk about an unknown circle and give it the variable name "A", or an unknown number and give it the variable name "x".
that mathematicians generally do not give mathematical objects very
descriptive, memorable or meaningful variable names. Usually the names are just
a single letter, like "A" or "x". Mathematicians do this
for two reasons:
1. They want the name to be as general and non-descriptive as possible.
2. They want the name to be easy to write, because they might have to write it many times.
Unlike mathematicians, scientists will sometimes give variables slightly more meaningful names, like "the temperature" and "the distance", because they are discussing more concrete or particular situations. In your economics course you'll probably see both of these sorts of variables used- both more meaningful variable names like "cost" and more abstract variable names like "x". In either case, it's important to know what particular sorts of objects these variable names are labelling. Whenever you come across a situation in your economics course where you don't know or aren't sure what a variable name is labelling, ask you professor.