The most unique Sound of Music tour
On vacation last month, I saw this tour bus. It illustrates a common problem with unique. According to Merriam-Webster, unique means sole or unequaled. A item either is unique, or it isn’t — there aren’t degrees to which an oil painting can be sole or unequaled, nor can a Halloween costume be more or less sole or unequaled than another.
In common usage, unique is applied to mean unusual: Goodness, her nail polish is rather unique, isn’t it? Under this definition, unique can be modified (somewhat unique, more unique, not very unique). Most dictionaries and grammar guides acknowledge that this can be and frequently is done, but it remains best practice to avoid modifying absolutes like unique in formal or professional use.