Many authors of usage guides, editors, teachers, and others feel strongly that such “absolute” words as complete, equal, perfect,
and especially unique
cannot be compared because of their “meaning”: a word that denotes an absolute condition cannot be described as denoting more or less than that absolute condition. However, all such words have undergone semantic development and are used in a number of senses, some of which can be compared by words like more, very, most, absolutely, somewhat,
and some of which cannot.
The earliest meanings of unique
when it entered English around the beginning of the 17th century were “single, sole” and “having no equal.” By the mid-19th century unique
had developed a wider meaning, “not typical, unusual,” and it is in this wider sense that it is compared: The foliage on the late-blooming plants is more unique than that on the earlier varieties.
The comparison of so-called absolutes in senses that are not absolute is standard in all varieties of speech and writing.
See also a1