comparator

noun

1. Any of various devices for comparing a physical property of two objects, or an object with a standard.

   “optical comparator”

2. An electronic device that compares two voltages, currents or streams of data.

   “electrical comparator”

   “digital comparator”

3. Anything that serves as a comparison.
4. A thing being compared against in the PICO process; often, a diagnostic method or a treatment being compared against another.

   “Roxanne Khazarian (“Plaintiff”) moved to compel discovery from Gerald Metals, LLC and Metals Trading Corp (“Defendants”), seeking the personnel file of Gary Lerner, an employee of Defendants. […] Defendants object to the production of these documents on the grounds that Mr. Lerner is not an appropriate comparator for Ms. Khazarian and his personnel file is therefore irrelevant.”

5. An application or program that compares prices, rates, tariffs of flights, smartphones, cars, etc.