only one

[Laowai]

Would you accept 'most unique' is good English?

[5jj]

I wouldn't, but you'll hear it.

[JohnParis]

Spoken, yes. Written, no.

What people say is often grammatically less than perfect. Maybe they want to add emphasis to something: "the most unique diamond I've seen in years", but while it sounds acceptable, it's still bad grammar.

Here is an interesting usage note from the Oxford Dictionary that answers your question to a "T":
USAGE: There is a set of adjectives—including unique, complete, equal, and perfect —whose core meaning embraces a mathematically absolute concept and which therefore, according to a traditional argument, cannot be modified by adverbs such as really, quite, or very. For example, since the core meaning of unique (from Latin ‘one’) is ‘being only one of its kind,’ it is logically impossible, the argument goes, to submodify it: it either is ‘unique’ or it is not, and there are no stages in between. In practice, the situation in the language is more complex than this. Words like unique have a core sense but they often also have a secondary, less precise (nonabsolute) sense of 'very remarkable or unusual,' as in : a really unique opportunity. It is advisable, however, to use unique sparingly and not to modify it with : very,: quite,: really, etc. Often, a writer can instead make accurate use of : rare,: distinctive,: unusual,: remarkable, or other nonabsolute adjectives.

John

[Laowai]

Thank you, the OED is the best. I wish I had access to it!

If spoken word is grammatically less than perfect, are the speakers at fault, or is the grammar shaky?

[Barb_D]

Whenever someone says "very unique" around me, my children invariably look at me to see if I physically wince. I'm working on my poker face.

[emsr2d2]

Thank you, the OED is the best. I wish I had access to it!

If spoken word is grammatically less than perfect, are the speakers at fault, or is the grammar shaky?

Why can't you get hold of the OED? Does your location have something to do with it? I've just looked on the BookDepository website and they have paperback copies of the full version for under £25. They also have the other versions (compact etc) at great prices.