| Acronym | Definition |
|---|
| S | Second(s) |
| S | South |
| S | Smile |
| S | Satisfactory |
| S | As |
| S | Search (Stores 100 code) |
| S | Sex |
| S | System |
| S | Source (transistor; electronics) |
| S | Store |
| S | Subject |
| S | Section |
| S | Save (baseball) |
| S | Super (in automatic transmissions; equal to 2) |
| S | Sign |
| S | Side (geometry, as in the SSS postulate) |
| S | Short |
| S | Safety (football) |
| S | Seite |
| S | Siemens |
| S | Secret |
| S | Sweden (ISO Country Identifier) |
| S | Storage |
| S | Savings (economics) |
| S | San Francisco, CA (mint mark) |
| S | Snow (weather reports) |
| S | Switch |
| S | Satellite (imagery, type of map) |
| S | Sin (Spanish: Without) |
| S | Sierra (aviation letter code) |
| S | Severe (rock climbing grade) |
| S | Stuttgart (auto license plate) |
| S | Semi-Annual |
| S | Smooth (woodworking) |
| S | Superb |
| S | Seminar |
| S | Scout |
| S | Sleeve |
| S | Sealed (CD condition) |
| S | Saskatchewan (postal code designation, Canada) |
| S | Sacrifice (baseball) |
| S | Senate |
| S | Sphere |
| S | Superman |
| S | Segment |
| S | Subsidiary (IRB) |
| S | Sheffield (postcode, United Kingdom) |
| S | Servicing |
| S | Sears (stock symbol) |
| S | Spectacles |
| S | Sickness (on overtime forms) |
| S | Sine (Latin: Without) |
| S | Scrap |
| S | Sequential |
| S | Shaman (Mic-O-Say, Heart of America Council, Boy Scouts of America) |
| S | Displacement |
| S | Seaman |
| S | Stokes (kinematic viscosity) |
| S | Sulfur |
| S | Shilling (British currency) |
| S | Spades (playing cards) |
| S | Soldering |
| S | Sparkasse (German: public savings bank) |
| S | Entropy (thermodynamics) |
| S | Starboard (nautical) |
| S | Subchapter S Corporation |
| S | Skype (voice-over-Internet service) |
| S | Security Prison (Cambodia; Khmer Rouge designation) |
| S | Serine (amino acid) |
| S | Systolic (peak blood pressure) |
| S | Streptococcus |
| S | Streptomycin |
| S | Antisubmarine (US military aircraft designation; as in S-2 Tracker) |
| S | Spaceplane (US military aerospace vehicle) |
| S | Schweizer Aircraft Co. (manufacturer's symbol) |
| S | Track spacing |
| S | Sacral Vertebra (prefix, as in S-1) |
| S | Scatterable (mines) |
| S | Socialdemokratiska Arbetarpartiet (Swedish political party) |
| S | Silicaceous (asteroid class) |
| S | Subthreshold Swing |
| S | Starboard Truss Segment (ISS) |
| S | Franchise Stamp (Scott Catalogue prefix; philately) |
| S | Fresnel Sine Integral |
| S | S Sub-Shell (innermost electron subshell) |
| S | Area of a geometric figure (mathematics) |
| S | TERCOM-Aided Inertial Navigation System |
| S | Onde Seconde (Italian: second wave; seismography) |
| S | Supervisory Function Bit |
| S | Secondary Body Waves |
| S | US DoT tire speed rating (112 mph) |
| S | Continuous-time complex variable (analogous to Z in discrete-time; electrical engineering) |
| S | Fourth Heartbeat Wave |