| S | South |
| s | Second (time) |
| S & T | Science and technology |
| S & TE | Support and test equipment |
| S x E | South by east |
| S x W | South by west |
| S-Band | 2 700 to 3 500 MHz |
| S-VHS | Super-video helical scanning |
| S/N | Signal-to-noise ratio |
| S1000D | AECMA Specification 1 000D |
| S2000M | AECMA Specification 2 000M |
| SA | Shock army |
| Simple alert |
| Surface-to-air |
| SAA | Small arms ammunition |
| SABA | Small agile battlefield aircraft |
| SAC | Standing armaments committee |
| Strategic Air Command |
| SACLOS | Semi-automatic command to line-of-sight |
| SADARM | Sense and destroy armour munition |
| SAE | Society of Automotive Engineers (USA) |
| SAG | Surface attack group |
| SAGE | Semi-automatic ground environment (system) |
| SAGW | Surface-to-air guided weapon |
| SALIS | Ship´s aircraft landing information system |
| SALM | Single anchor leg mooring |
| SALT | Strategic arms limitation talks |
| SAM | Surface-to-air missile |
| SAMHADS | Submarine automatic message-handing and -distribution system |
| SAMI | Speed of approach measuring instrument |
| SAMOS | Satellite and missile observation system |
| SAN | Storage area network (data) |
| SAP | System alignment procedure |
| SAPP | Special airfield pavement programme |
| SAR | Search and rescue |
| Synthetic aperture radar |
| SARBE | Search and rescue beacon equipment |
| SARPS | Standards and recommended practices (ICAO) |
| SARSAT | Search and rescue satellite-aided tracking |
| SART | Search and rescue transponder |
| SAS | Special Air Service |
| Special ammunition storage |
| SASP | Special ammunition supply point |
| SAT | Saturated air temperature |
| Small arms trainer |
| satcoms | Satellite communications |
| satnav | Satellite navigation |
| SAU | Surface attack unit |
| SAW | Surface acoustic wave |
| SBAC | Society of British Aerospace Companies |
| SBC | Single board computer |
| SBDA | Short-duration breathing apparatus |
| SBE | Standby engine |
| SBM | Single-buoy mooring |
| SBS | Special Boat Service (Royal Marines) |
| SC | Scan converter |
| Semiconductor |
| Steering committee |
| Sub-committee |
| SCA | Speed control adviser |
| SCAD | Self-contained automatic fire detection system |
| SCADA | Supervisory control and data acquisition |
| System control and data acquisition |
| SCART | Syndicat des Constructeurs d´Appareilles Radio Récepteurs et Téléviseurs (cable) |
| SCAS | Supply control and accounting section |
| SCBA | Self-contained breathing apparatus |
| SCD | Security coding device |
| SCL | Standard conventional load |
| SCM | Supply chain management |
| SCOR | Scientific Commission on Ocean Research (UN) |
| SCPS | Survivable collective protection system |
| SCR | Silicon-controlled rectifier |
| SCRA | Single channel radio access |
| SCRDE | Stores Clothing Research and Development Establishment |
| SCSI | Small computer system interface |
| SD | Suction dredger |
| SDA | Ship destination authority |
| SDBA | Short-duration breathing apparatus |
| SDE | Shared data environment |
| Software development environment |
| SDI | Strategic defence initiative (USA) |
| SDL | Standard distribution list |
| SDLC | Synchronous data link control |
| SDMS | Support defence missile system |
| SDO | Staff duty officer |
| SDR | Software-defined radio |
| Special drawing right |
| Strategic defence review |
| SDRAM | Synchronous DRAM |
| SDSL | Symmetrical digital subscriber line |
| SE | South-east |
| Support equipment |
| SE x E | South-east by east |
| SE x S | South-east by south |
| SEAD | Suppression of enemy air defences |
| SEC | Spoiler and elevator computer |
| sect | Section |
| SED | Surface-conduction emission display |
| selcal | Selective call system |
| SEM | Scanning electron microscope |
| SEP | Safety and emergency procedures |
| Selective employment plan |
| Self-elevating platform |
| SERC | Science and Engineering Research Council |
| SERS | Surface enhanced Raman spectroscopy |
| SES | Ship earth station |
| Surface effect ship |
| SESAME | Supply executive system and automated management environment |
| SET | Science, engineering and technology |
| Secure electronic transaction |
| SEV | Surface effect vehicle |
| SEWS | Satellite early warning system |
| SF | Special Forces |
| SF6 | Sulphurhexafluoride |
| SFC | Specific fuel consumption |
| SFDC | Shop floor data collection |
| SG | Specific gravity |
| SGML | Standard generalised markup language |
| SGT | Satellite ground terminal |
| SH | Support helicopter |
| SHA | Sideral hour angle (nav) |
| SHAM | Sideral hour angle of observer´s meridian |
| SHAMS | Sideral hour angle of mean sun |
| SHAPE | Supreme Headquarters Allied Powers in Europe |
| SHAS | Sideral hour angle of star |
| SHATS | Sideral hour angle of true sun |
| SHF | Super-high frequency (above 3 000 MHz) |
| Shippos | Ship position reporting service |
| SHOL | Safe helicopter operation limits |
| SHORAD | Short-range air defence |
| SHORADEZ | Short-range air defence engagement zone |
| shp | Shaft horse-power |
| SI | Standardisation and interoperability |
| Système International d´Unités (International System of Units) |
| SIAM | Self-initiated anti-aircraft missile |
| SIB | Special Investigation Branch |
| SIC | Silicon integrated circuit |
| Subject indicator code |
| SID | Standard instrument departure |
| Sudden ionospheric disturbance |
| SIDE | Sector input and display equipment |
| SIF | Selective identification feature (radar) |
| sig | Signal |
| sigint | Signal intelligence |
| sigmet | Significant meteorological information |
| sim | Simulation |
| SIMD | Single instruction, multiple data |
| SIMM | Single in-line memory module |
| SIMS | Secondary ion mass spectrometer |
| SINS | Ship identification number scheme |
| Ship inertial navigation system |
| SIP | Separate initial provisioning |
| SIPRI | Stockholm International Peace Research Institute |
| SIRE | Ship inspection report |
| SIRS | Support information retrieval system |
| SIS | Shipping information service |
| SIT | Spontaneous ignition temperature |
| sit | Situation |
| SITA | Societé Internationale de Télécommunications Aériennes (International Society of Aviation Telecommunications) |
| sitpro | Simplification of international trade procedures |
| SITREP | Situation report |
| SITS | Standard international trades classification (UN) |
| SLAET | Society of Licensed Aircraft Engineers & Technologists |
| SLAM | Stand-off land-attack missile |
| SLAP | Slot allocation program |
| SLAR | Side-looking airborne radar |
| SLBM | Submarine-launched ballistic missile |
| SLCM | Sea-launched cruise missile |
| SLEP | Slimline equipment practice |
| SLF | Standard linear format (geo) |
| SLINS | Ship laser inertial navigation system |
| SLIR | Sideways-looking infra-red |
| SLOC | Sea lines of communication |
| SLR | Self-loading rifle |
| SLRR | Sideways-looking reconnaissance radar |
| SLS | Side lobe suppression (radar) |
| SLSI | Super-largescale integration |
| SM | Scatterable mine |
| Shipping master |
| SMA | Shape memory alloy |
| SMART | Self-monitoring analysis and reporting technology |
| SMC | Sheet-moulding compound |
| Surface movement control |
| SMD | Supply management data |
| SMEs | Small- and medium-sized enterprises |
| SMGCS | Surface movement guidance and control system |
| SMIL | Synchronised multi-media integration language |
| smk | Smoke |
| SMO | Senior medical officer |
| SMP | Shape memory polymer |
| SMR | Surface movement radar |
| SMS | Short message system |
| SMT | Ship´s mean time |
| Surface-mount technology |
| SMTP | Simple mail transfer protocol (email) |
| SMWP | Special minimum weather provisions |
| SNF | Short-range nuclear forces |
| SOA | Speed of advance (over the ground) |
| SOAP | Single object access protocol (computing) |
| SOC | Statement of compliance |
| SOHO | Small office, home office |
| Solar and Heliospheric Observatory |
| SOI | Signal operation instructions |
| Silicon on insulation (chip) |
| Southern oscillation index (met) |
| Start of installation |
| Statement of operating intent |
| SOJ | Stand-off jamming |
| SOLAS | Safety of life at sea (international convention) |
| sonar | Sound navigation and ranging |
| SOP | Standard operating procedure |
| SOR | State of readiness |
| SOS | Save our souls (emergency call) |
| Silicon on sapphire (microchip) |
| SOTAS | Stand-off target acquisition system |
| SOW | Statement of work |
| SP | Self-propelled |
| Sub-panel |
| SPA | Submarine patrol area |
| SPADATS | Space detection and tracking system |
| SPAR | Seagoing platform for acoustic research |
| spec | Specification |
| SPG | Self-propelled gun |
| Stockpile planning guidance |
| SPHVM | Self-propelled high-velocity missile (system) |
| SPI | Smart procurement initiative |
| SPIS | Services packing instruction sheet |
| SPM | Scanning proton microprobe |
| Single-point mooring |
| SPOC | SAR point of contact |
| SPOT | Small personal objects technology |
| SPRITE | Signal processing in the element (infra-red video) |
| SPS | Secondary power system |
| Standard positioning service (GPS) |
| SPST | Single-pole single-throw (switch) |
| SQ | Special quality (steel cable) |
| SQC | Statistical quality control |
| SQL | Structured query language (computer) |
| Sqn | Squadron |
| SQUID | Superconductive quantum interference device |
| SR | Strategic reserve |
| SRA | Special rules air space |
| Surveillance radar approach |
| SRAAM | Short-range air-to-air missile |
| SRAM | Short-range attack missile |
| Static random access memory |
| Structural radar-absorbent material |
| SRARM | Short-range anti-radiation missile |
| SRBM | Short-range ballistic missile |
| SRD | System requirements document |
| SRE | Single-round effectiveness |
| Sound reproduction equipment |
| Surveillance radar element of GCA |
| SRM | Single-role mine hunter |
| Supplier relations management |
| SRMH | Single-role mine hunter |
| SRN | System reference number |
| SRR | Short-range recovery (helicopter) |
| SRS | Satellite radar station |
| SRSOM | Short-range stand-off missile |
| SRT | Short-range transport (aircraft) |
| Strategic rocket troops |
| SRZ | Special rules zone |
| SS | Sea state |
| Special survey |
| Stainless steel |
| Steam ship |
| Surface-to-surface |
| SSA | Sector safe altitude |
| Ship Support Agency |
| Software support analysis |
| SSADM | Structured system analysis and design method (software) |
| SSB | Single side-band (radio) |
| Suppressed side-band |
| SSC | Semi-submerged catamaran |
| SSCDS | Small ship combat direction system |
| SSD | Slow-speed diesel |
| SSE | South-south-east |
| SSFC | Sequential single-frequency code |
| SSFDC | Solid-state floppy disc card |
| SSGW | Surface-to-surface guided weapon |
| SSI | Small-scale integration |
| SSJ | Self-screening jamming |
| SSKP | Single-shot kill probability |
| SSM | Spread spectrum modulation (radio) |
| Surface-to-surface missile |
| SSMA | Spread spectrum multiple access |
| SSP | Scheduled strike programme |
| Semi-submerged platform |
| Storage service provider (data) |
| SSPU | Ship´s service power unit |
| SSR | Secondary surveillance radar |
| SSS | Semi-submerged ship |
| Ship-shore-ship (communications) |
| SSSB | Ship-shore-ship buffer |
| SSSI | Software support significant item |
| SSSR | Selective secondary surveillance radar (Mode S) |
| SST | Sea surface temperature |
| Special strike teletype |
| Supersonic transport (aircraft) |
| SSTV | Slow-scan television |
| SSV | Soft-skinned vehicle |
| SSW | South-south-west |
| ST | Spring tide |
| Steam turbine |
| Strategic transport (aircraft) |
| Support tank |
| STA | Surveillance and target acquisition |
| Stanag | Standardisation agreement (NATO) |
| STAR | Standard terminal arrival route |
| Starec | Status recording system |
| START | Strategic arms reduction talks |
| STAS | Short-term air supply |
| stat | Static |
| stats | Statistics |
| STB | Standard test band (radio) |
| stbd | Starboard |
| STC | Sensitivity time control |
| Support tank, command |
| STCW | Standards of Training and Certification of Watchkeepers |
| STD | Standard |
| Subscriber trunk dialling |
| Std T | Standard time |
| STE | Software test environment |
| STEM | Scanning transmission electron microscope |
| STEP | Standard for exchange of product data |
| STM | Scanning tunnelling microscope |
| STN | Super-twist nematic (LCD) |
| STOL | Short take-off and landing |
| STOVL | Short take-off and vertical landing |
| STP | Standard temperature and pressure |
| STS | Ship-to-ship |
| STU | Secure telephone unit |
| SUIT | Sight unit, infantry, Trilux |
| SUM | Surface-to-underwater missile |
| supps | Regional supplementary procedures |
| SUS | Sound underwater signals |
| SUSAT | Sight unit, small arms, Trilux |
| SV | Sailing vessel |
| SVE | Secure voice equipment |
| SVFR | Special visual flight rules |
| SVGA | Super video graphics array |
| SW | Salt water |
| Sea water |
| Shipper´s weight |
| Shortwave |
| South-west |
| Special weapon |
| SW x S | South-west by south |
| SW x W | South-west by west |
| SWAT | Special weapons and tactics |
| SWATH | Small waterplane area twin-hull (ship) |
| SWG | Standard wire gauge |
| SWHQ | Static war headquarters |
| SWL | Safe working load |
| Statutory water level |
| SWSA | Ship weapon system authority |
| SWSE | Ship weapon system engineering |
| swy | Stop way |
| SY | Steam yacht |
| SYMES | Systematic machinery and equipment selection |
