In medicine and statistics, a<unk> test is usually the diagnostic test or benchmark that is the best available under reasonable conditions. Other times, a<unk> is the most accurate test possible without restrictions. Both meanings are different because for example, in medicine, dealing with conditions that would require an autopsy to have a perfect diagnosis, the<unk> test would be the best one that keeps the patient alive instead of the autopsy.
Gold standard 
Absolute threshold
Relative biological effectiveness
Reference dose
Therapeutic index
Candidate of Medicine
Real world evidence
Universal design