It basically signifies that one is discussing price specifically in terms of how it relates to the demand curve.
If I had to guess, I'd say its gratuitous use probably started with conversations between corporate executives and accountants where the term was being used precisely, moving from there to other executives who were at the meeting, didn't understand the term but thought it sounded good and so tried to imitate the people who knew what they were talking about, gradually spreading out into the culture from there. So, yeah, fundamentally people imitating each other to try to sound clever.
Both gay and homosexual can be used for both sexes, and they mean mostly the same thing; the differences are subtle.
Probably because the word lesbian exists as well, one is slightly more likely to refer to men when using the word gay; but note that it is very often also used for women. When used as a noun, gay seems to refer to men a bit more often than as an adjective, although it is still very often used to refer to both men and women. It rather depends on context. The word homosexual seems to be completely gender-neutral.
Gay is more informal: homosexual is more formal, and so it is more likely to be used in e.g. medicine and biology. As a consequence, using homosexual can sometimes sound a little bit as if you were describing patients, as if it were some mental illness. This effect is not very strong or ubiquitous, but it is sometimes there. It is stronger when used as a noun (an homosexual, homosexuals). Note that gay is currently in the process of being used more in formal contexts too.
The word homosexual is older. Because homosexuality was long treated as a disease or at least as undesirable, some of this old negativity still clings to the word homosexual, especially as a noun. It is as if you were referring to the past, although this effect, too, is not that strong.
I think this is also the reason why the word gay came to be used (around the 1960s? earlier?) to refer to homosexuals: they wanted a more positive-sounding word. You will find that most gays will mainly use gay, except in a scientific context; and even there, homosexual as a noun has become almost impossible. If you were to say homosexuals, and you weren't over 50 or a bit reactionary in general, I would think you were joking.
Best Answer
Both the teachers are correct, in different situations. You cannot dispute with someone, but you can get into a dispute with them, or you can argue with them.
You can use dispute as a verb when you're talking about inanimate objects (including but not limited to law or politics), but it doesn't make sense to use when the object is another person.
Last but not least, there are cases where it may look like the object is a person, but really it's a person's idea or position (ideas being inanimate objects).