The IACS Taxonomy Definition of Terms for ISA/IEC 62443
The Industrial Automation and Control System (IACS) Taxonomy Definition of Terms is a short, two-page .pdf glossary that explains the meaning behind some frequently used terms in the series.
It was created to help build a common basis of understanding for anyone reading or seeking to use the 62443 standards.
https://gca.isa.org/blog/the-iacs-taxonomy-definition-of-terms-for-isa/iec-62443