Certain UN Regulations and UN GTR, including texts under development, include terms, definitions, and classifications relating to vehicle powertrain systems (e.g., electric vehicle, fuel cell vehicle), energy storage systems (e.g., fuel tank, gas cylinder, battery), and energy converter (e.g., internal combustion engine, fuel cell, electric machine). However, the definition of these terms varies across the regulations which can lead to confusion and inconsistencies in the application of regulatory requirements. Mutual Resolution No. 2 is intended as a repository for terms, acronyms, and definitions towards ensuring their uniform use across regulations.