definitive
adj.adj. the best or most complete version of something that cannot be improved. It can also describe a final decision that no one can change.
adj. providing a final solution or end to a situation; representing the most authoritative or comprehensive example of its kind. Often used to describe academic works or legal rulings.
This is the definitive guide to local birds.
The court's ruling provided a definitive answer to a legal question that had been debated for decades.
After years of conflicting reports, the professor published what is now considered the definitive biography of the explorer, utilizing previously undiscovered private journals to settle several historical disputes.
From Middle French définitif.
Typically used before a noun to indicate authority or finality.
the most definitive versionthe definitive versionDefinitve is often considered a non-gradable adjective; something is either the final, authoritative version or it is not.