comparator

noun5

1. •
   Any of various devices for comparing a physical property of two objects, or an object with a standard.
2. •
   An electronic device that compares two voltages, currents or streams of data.
3. •
   An application or program that compares prices, rates, tariffs of flights, smartphones, cars, etc.
4. •
   Anything that serves as a comparison.
5. •
   A thing being compared against in the PICO process; often, a diagnostic method or a treatment being compared against another.