unique
adjective
uk/juːˈniːk/ ussomething that is unique is unusual or the only one of its type:
Fast-growing companies are in a unique position to attract the best candidates.
Over the past 15 years, she has made a unique contribution to the country's business environment.
a unique opportunity/set of circumstances
a unique problem, challenge, etc. is difficult to deal with because it has never happened before:
The recent financial crisis has posed some unique challenges for governments.
if something is unique to a place or situation, it only exists in that place or situation:
Many of our problems are unique to our profession.