IEC 60194-1:2021 covers terms and definitions closely related with TC91 technology. This document, together with IEC 60194-2:2017, cancel and replace IEC 60194:2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: 1) exclusion of 32 general terms better served by other TCs; 2) exclusion of 47 terms no longer used by the electronic assembly industry; 3) inclusion of 14 new terms related with device embedded substrate technology; 4) inclusion of 113 synonymous terms; 5) removal of identification codes for terms and annexes.