All but one of the books I've ever read use the definitions I gave; however, I vaguely recall the kids I tutor using a book that used different definitions. Seems like it was only this year or last year. I'm tempted to think that either the textbook author just didn't bother checking up before writing the book or the author is older and using a definition he learned back in ancient times.

Either way, I prefer "positive", or "non-negative", etc. Less ambiguous. And I know now when I read the terms, I need to find where the author defines them or where he has used them in a way that the meaning is clear.