Can I Copy Geometry Terms and Postulates?

Dear Rich: I would like to produce and sell a reference sheet for definitions, postulates and theorems used in high school geometry. I am wondering if these are copyrighted. I was looking through several textbooks, math encyclopedias and even websites, and I found that some of these terms were identical and others had slight variations. It almost seems as though there would be a standard for these terms that should be used in teaching all math so that students are learning the same definitions, etc. no matter where they are educated. A postulate (or axiom) is a statement that assumes the existence, fact, or truth of something, for example -- all right angles are equal to one another. A theorem is a result that has been proved to be true (using facts that were already known) for example -- the Pythagorean Theorem. Most likely you're free to borrow postulates and theorems without legal consequence. Because postulates and theorems are ideas (or part of a geometry system or method) they are not likely to be protected. As the Copyright Office has stated, protection is not granted for "ideas, procedures, methods, systems, processes, concepts, principles, discoveries, or devices (as distinguished from a description, explanation, or illustration)."
Definitions. A definition is a statement of the meanings of words or phrases. As a general rule, if there is a limited number of ways to express a definition, copyright law tolerates copying. Short definitions may fall into this category. If not, a few changes in wording should suffice. However, be careful when you take too many word-for-word explanations from one source. The source may complain that you are infringing original expression (that is, they may argue that there are many ways to  define the term) or you may be accused of "compilation" infringement.