What is the difference between these phrases? When is it valid to use which? Should they be avoided as being ambiguous?
Nothing but A
Means only A. You don't want anything else.
Anything but A
Means that you don't want A. You could have B or C, or maybe even both B and C (and even E if someone offers) - but NOT A!
Everything but A
Means that A is the only thing you don't want. You do want the rest of the entire alphabet - but NOT A!
"Nothing but" means "only":
- Nothing but the best.
- Only the best.
"Anything but" means any one thing except whatever follows but:
- Don't make me go to school. Anything but that.
- Don't make me go to school. You can make me do anything else, but don't make me go to school.
"Everything but" means everything excepting whatever follows but:
- He remembered to bring everything but his toothbrush.
- He brought everything with him except his toothbrush, which he left behind.
But here means except.
I want nothing but chocolate
means I do not want to have any food except chocolate.
Give me anything but chocolate
means I can eat all kinds of food except chocolate.
I will eat everything but the chocolate
means I am going to have all the food in front of me except the chocolate.
Nice to see I'm not the only one pondering this. The above answers do sum up the most frequent usages, but I would like to propose an addendum concerning the ambiguity of the phrases, which, for me, was the core of the question:
"Anything but" may sometimes also be used in a way that is closer in meaning to "nothing but", mainly when posed as a rhetorical question, as in:
"How can B mean anything but A?" — implying that B means A, and only A.
This does not call for avoidance of the phrase, however, as the intended meaning can, more or less, be easily understood from the context of its use. Give readers/listeners some linguistic credit.