Standard

Something used as a measure, norm, or model in comparative evaluations.
1. An accepted measure which can be
used for comparison;
2. Serving as an accepted measure.

In metrology (the science of measurement), a standard (or etalon) is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are the fundamental reference for a system of weights and measures, against which all other measuring devices are compared. Historical standards for length, volume, and mass were defined by many different authorities, which resulted in confusion and inaccuracy of measurements. Modern measurements are defined in relationship to internationally standardized reference objects, which are used under carefully controlled laboratory conditions to define the units of length, mass, electrical potential, and other physical quantities.

Sources:

Lexico Oxford English and Spanish Dictionary, Thesaurus, and Spanish to English Translator. www.lexico.com.

Nick Brieger, Alison Pohl: Technical English Vocabulary and Grammar.

Phillip Ostwald,Jairo Muñoz, Manufacturing Processes and Systems (9th Edition)John Wiley & Sons, 1997 ISBN 978-0-471-04741-4.