E2s

E2s is a label used for several unrelated items that share the E2 designation. It functions as a shorthand in different fields rather than indicating a single, unified concept.

In transportation, the E2 Series refers to a family of high-speed Shinkansen trainsets operated by JR East in Japan. Introduced in the early 2000s, the E2 Series trains are designed for rapid intercity service, featuring aluminum bodies and modular configurations to accommodate variable passenger loads.

In aviation, the E-2 Hawkeye is a carrier-based airborne early warning and control aircraft used by the United States Navy and other operators; E-2s denotes multiple units of this aircraft. The aircraft carries a distinctive radar dome and provides early detection and battle management for carrier groups.

In signaling and safety, E2S is a brand of warning devices including audible alarms and visual indicators. E2s may refer to installations or products in this line used for industrial or public safety warning systems.

In physics, E2 denotes an electric quadrupole transition; E2s (plural) refer to such transitions between energy levels in atoms, ions, or nuclei. These transitions are typically weaker than electric dipole (E1) transitions and are studied in spectroscopy and related areas. The term appears in various technical contexts, reflecting its role as a conventional label rather than a single domain of knowledge.