S4, S 4, Š-4, S.4 or S-4 may refer to: People S4 (Dota player), Gustav Magnusson, Swedish Dota 2 player S4 (military), a logistics officer within military units Places County Route S4 (California), a road in San Diego, California Science and mathematics Mathematics S4 algebra, a variety of modal algebras, also called Interior algebra Symmetric group S4 (S4), an abstract mathematical group S4, a normal modal logic Chemistry S4: Keep away from living quarters, a safety phrase in chemistry Tetrasulfur (S4), an allotrope of sulfur Biology Fourth heart sound, or S4, an abnormal heart sound often indicative of congestive heart failure or cor pulmonale Fourth sacrum of the vertebral column in human anatomy Sacral spinal nerve 4, a spinal nerve of the sacral segment Technology S (programming language) version 4 Hibernation a sleeping state in a computer SG2 Shareable (Fire Control) Software Suite (S4) Nikon Coolpix S4, a camera Samsung Galaxy S4, a smartphone Samsung Galaxy S4 Mini, a mini version of the Samsung Galaxy S4 Samsung Galaxy Tab S4, an Android tablet Transportation Routes S4 (Berlin), an S-Bahn line S4 (Munich), an S-Bahn line S4 (Nuremberg), an S-Bahn line S4 (Rhine-Main S-Bahn), an S-Bahn line S4 (Rhine-Ruhr S-Bahn), an S-Bahn line S4 (St. Gallen S-Bahn), an S-Bahn line in Switzerland S4 (RER Vaud), an S-Bahn line in Switzerland S4 (ZVV) line S4, a line of the S-Bahn Zürich in Switzerland Bremen S-Bahn line S4 Hanover S-Bahn line S4 Rhine-Neckar S-Bahn line S4 Rostock S-Bahn line S4, a 2010-planned future line Stadtbahn Karlsruhe line S4 Stuttgart S-Bahn line S4 S4, a line of the Brussels Regional Express Network Vehicles Alco S-4, a locomotive Audi S4, a car Lancia Delta S4, a 1984 Group B rally car Hydra Technologies Ehécatl, S4, a Mexican unmanned aerial vehicle Letov Š-4, a 1923 Czechoslovak aircraft Prussian S 4, an 1894 steam locomotives class Seibel S-4, a 1951 helicopter Supermarine S.4, a 1925 British seaplane USS S-4 (SS-109), a 1919 US Navy submarine Groups, companies, organizations S04, FC Schalke 04, a German professional sports club Shift4 Payments, a U.S. payment processor SATA International (IATA airline designator "S4"), Azores Airlines Other S4 (classification), a disability swimming classification Form S-4, a form required by the Securities and Exchange Commission to declare mergers and acquisitions S4 standard, a set of standards for model railways (P4 gauge) See also SSSS (disambiguation) 4S (disambiguation) S (disambiguation) 4 (disambiguation)