Some Adjectives Cannot Be Graded, and "Very Unique" Is Why People Argue

Write very unique in a document and somebody will correct it. Ask them why, and the answer is usually a confident restatement rather than an explanation: because unique means one of a kind.

That is correct as far as it goes, but it explains only one word. The real pattern is larger and more useful.

Two kinds of adjective

Gradable adjectives describe qualities that come in degrees. Something can be slightly warm, quite warm, very warm, unbearably warm. They take intensifiers, they form comparatives, and they answer how much?

Non-gradable adjectives describe states with no middle. Either a thing is or it is not. There is no quite dead, no slightly pregnant, no rather nuclear.

Non-gradables come in two flavours:

Absolute — the quality is total by definition: dead, unique, perfect, impossible, infinite, complete, universal.
Classifying — the adjective sorts a thing into a category rather than describing a degree: nuclear, wooden, digital, annual, chemical, married. A reaction is chemical or it is not. Nothing is very chemical.

The intensifiers change too

This is the part that is genuinely useful and rarely taught. Non-gradable adjectives do take modifiers — just not the same ones.

Gradable take very, quite, rather, extremely, fairly, a bit, slightly: very cold, rather difficult, slightly damp.
Non-gradable take absolutely, completely, totally, utterly, entirely, virtually, almost: absolutely impossible, completely destroyed, virtually unique.

So very unique grates not because unique refuses modification, but because it has been handed the wrong sort. Almost unique and virtually unique are both unobjectionable, and both say something precise: not quite one of a kind, but close.

The same test works throughout. Very freezing is odd; absolutely freezing is idiomatic. Very exhausted is odd; completely exhausted is normal. Once you notice which intensifier a word wants, you can often identify its type without thinking about definitions at all.

Where it gets genuinely contested

Several absolutes have been used comparatively by good writers for centuries, and this is where the confident corrections start to look shaky.

The Preamble to the United States Constitution begins in order to form a more perfect Union. If perfect were strictly absolute, that phrase is nonsense — and it was written by people not known for careless drafting.

What is happening is that these words have two senses. There is the strict logical sense — flawless, one of a kind — and a looser everyday sense meaning something like remarkable or very good indeed. In the looser sense, grading is perfectly natural, and it is the sense most speakers reach for most of the time.

Merriam-Webster records both senses for unique and notes that the graded use is long established. It is not an error. It is a usage that a portion of educated readers dislike — which is a different thing, and worth keeping separate in your head.

What to do about it

The practical position is not the rule is fake, ignore it. It is this: the strict reading costs you nothing, and the loose reading costs you some readers.

If you mean one of a kind, write unique and let it stand alone. It is stronger without the intensifier anyway — very almost always weakens the word it is propping up.

If you mean unusual, write unusual, or remarkable, or distinctive. You will have said what you meant more precisely and avoided the argument entirely.

And if you genuinely mean close to one of a kind, almost unique is available, correct, and precise. It is the option nobody remembers.

The useful test

Before modifying any adjective, ask whether the quality has a middle. Can something be half of it? If yes, very is fine. If no, reach for absolutely or almost — or, better, trust the word to carry its own weight and drop the intensifier altogether.