For
grammar nuts, the word unique is very
interesting because it is the canonical example of an
absolute grammatical term. It is unable to be modified by any adverb or used in a
quantitative comparison. Either a thing can be described as unique or it cannot. A thing cannot be
very unique,
strikingly unique,
more unique than a breadbox,
less unique than a ham sandwich -- or anything other than
unique. Or as Midori suggests: perhaps
everything is unique.
Dictionary.com tells it like this: " . . . unique is the paradigmatic absolute term, a shibboleth that distinguishes between those who understand that such a term cannot be modified by an adverb of degree or a comparative adverb and those who do not."
Other so-called absolute terms are absolute, chief, complete, perfect, prime, equal, and parallel -- although in non-mathematical usage the last three have a little wiggle room.