Standard
1. Standard – in a broad sense – the sample, the standard, the model adopted for the original for comparison with other similar objects.
2. A standard is a reference that is used to calibrate measurements.
There are different levels of standards for physical measurements. The master standards or primary standards are those of the highest quality, which define their unit of measure. The next level of standards in the hierarchy is secondary standards, which are calibrated with reference to a primary standard. The third level of the hierarchy encompasses the working standards. Working standards are periodically calibrated from a secondary standard.
There are also laboratory standards, which are defined by national organizations to certify and calibrate labs and educational facilities. Because laboratory standards are used as a reference and are held to a quality standard, they are sometimes (incorrectly) referred to as secondary standards. However, that term has a specific and different meaning.
Словник Webster's Dictionary https://www.merriam-webster.com/
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved
ThoughtCo. Dictionary https://www.thoughtco.com/definition