Are 'rich' and 'cold' relative or absolute terms? I said to my boss yesterday, ‘Man, it's cold out!’ He said, ‘Cold is a relative term.’ He has also said that 'rich' is a relative term. If that's the case, then it seems that all terms can be relative, right? I truly don't understand this at all.
In a logic sense, yes, these terms are relative. And determining the truth of an assertion that Fellow X is rich might require discussions about what this means for each person.
But in a language sense, if you say someone is rich you are asserting an fact and not being comparative. If I say "He is richer" this is an incomplete statement until someone specifies who else he is being compared to. It is the same as saying "He has a yellow shirt". Nobody is going to say this is relative because there's more than one shade of yellow in the world.
My understanding is that this use of "relative term" is informal and not any kind of rule that you need to worry too much about. In effect, anything without a defined point of reference, that could be interpreted differently to different people, could be said to be a relative term.
The issue with saying "It's cold outside" is that it could mean different things to different people. Living in the UK, what I consider cold could be warm to somebody living in Scotland. What they consider cold could be warm to someone living in Greenland.
To remove any doubt, you could add a frame of reference:
In the kind of informal situation you described, I really wouldn't worry about whether a term is "relative" or "absolute". People will assume that you mean either "it's colder than usual" or "it's cold for me" and understand your intent.
As a side note, in formal situations, you'd want to avoid this entirely by just being precise.
Finally, as a matter of opinion, I'd guess that your boss wasn't so much saying that the comment was wrong because it was a relative term, but rather trying to make a joke out of the situation.
Einstein said everything is relative.
What your boss meant was not a linguistic thing, but simply that what can feel as cold for you, might feel not so cold for someone who is used to -50 degree winters.
What a poor person images as "being rich" might appear to a millionaire as destitution.
It is a common way of saying
You could point at a nice big limousine and say "that is a nice big car!", and a truck driver who just parked his 20 tonne truck could say "well, big is a relative thing."
Now as for the linguistic part, some adjectives are indeed absolute. That means you can not have them more or most, you have them or not. Cold and rich are not examples of this by the way, as you have richer / richest and colder / coldest.
Although some people will say something is more perfect or optimal than something else, or they will look for the most optimal solution, that use is generally considered incorrect.
As for pregnant, I think you can see that someone is not a bit pregnant, or more pregnant than another.
Those adjectives are not relative. Of course, in poetry or other specific stylistic situations, you will find them being used as relative sometimes, but not in general written or spoken English.