IEC TS 62600-1:2020 defines the terms relevant to ocean and marine renewable energy. For the purposes of this Technical Specification, sources of ocean and marine renewable energy are taken to include wave, tidal current, and other water current energy converters. This Technical Specification is intended to provide uniform terminology to facilitate communication between organizations and individuals in the marine renewable energy industry and those who interact with them. This second edition cancels and replaces the first edition published in 2011, and its Amendment 1, published in 2019. This edition includes the following significant technical changes from the previous edition: – Approximately 45 % of the original terms which were either not in use, used only in a glossary sense, or which are commonly understood and found in other references were removed. – Thirteen (13) terms considered more general than tidal were moved up from IEC TS 62600-200 and added. – Eight (8) terms that were added in Amendment 1 to IEC TS 62600-1 were incorporated alphabetically. – Six (6) additional new terms were added.