| S |
| S | Non-Refigerated Rations |
| S | Secret |
| S Maneuver | A weave in a horizontal plane. |
| S&D | Search and Destroy |
| S&T/S&TC | Supply and Transportation/Center |
| S/ND | Secret/No-Foreign Dissemination |
| S/NF | Secret/No Foreign Dissemination |
| S/O | Stockage Objective |
| S/T | Short Ton |
| SA | Senior Advisor |
| SA | Small Arms |
| SA | Surface to Air |
| SA-2 | Soviet surface-to-air missile system |
| SA-7 | Soviet manufactured Surface to Air Missile |
| SA/AB | Army Advisory Detachment Airborne Division |
| SA4CZ | Army Advisory Group - IV Corps Tactical Zone |
| SAAFO | Special Assistant to the Ambassador for Field Operations |
| SAALC | San Antonio Air Logistics Center |
| SAAM | Special Assigned Airlift Mission |
| SAAMA | San Antonio Air Material Area |
| SAB | Scrap Ammunition Brass |
| SAC | Strategic Air Command |
| SACADVON | Strategic Air Command Advanced Echelon |
| SACMD | Senior Army Advisor Capitol Military District Special Zone |
| SACSA | Special Assistant for Counterinsurgency and Special Activities |
| SAE | Staff Advisory Element |
| SAEDA | Subversion and Espionage Directed Against the United States Government |
| SAFE | Selected Areas for Evasion |
| SAFFO | Special Assistant to the Ambassador for Field Operations (United States Mission) |
| SAFOI | Secretary of the Air Force, Office of Information |
| SAM | Space Available Mail |
| SAM | Special Air Mission |
| SAM | Surface-to-Air Missile |
| SAME | Senior Advisor's Monthly Evaluation |
| SAMOB | Surface to Air Missile Order of Battle |
| SAPOV | Sub-Area Petroleum Office, Vietnam |
| SAR | Sea-Air-Rescue |
| SAR | Search and Rescue |
| SAS | Special Air Service |
| SASIA | Southeast Asia |
| SASP | Security Assistance Surveillance Program |
| SATCOM | Satellite Communications |
| SATP | Security Assistance Training Program |
| SATS | Short Airfield Tactical Strip |
| SAW | Special Air Warfare |
| SB | Special Branch |
| SBD | Signal Base Depot |
| SC | Signal Corps |
| SCAG | Saigon Civil Assistance Group |
| SCAN-ODD | MIG airborne intercept radar |
| SCARWAF | Special Category Army with Air Force |
| SCATTOR | Small Craft Assets, Training and Turnover of Resources |
| SCD | Special Collection Department |
| SCH | School |
| Scissors | Defensive maneuver in which a series of turn reversals are executed in an attempt to achieve offensive after an overshoot by the attacker. |
| SCP | Special Collection Program |
| SCR | Special Commissariat of Refugees |
| SCRF | Small Craft Repair Facility |
| SCT | Special Commando Team |
| SCU | Special Commando Unit |
| SCUBA | Self Contained Underwater Breathing Apparatus |
| SD | State Department |
| SD | Subdistrict |
| SDC | Self-Defense Corps |
| SDS | Supplemental Data Sheet(s) |
| SE | Southeast |
| SEA | Southeast Asia |
| SEA LORDS | Southeast Asia Lake-Ocean-River-Delta Strategy |
| Sea Wolf | UH-1 Helo, Heavily Armored, USN operated. |
| SEA-ATS | Southeast,Asia Automatic Telephone System |
| SEAC | Southeast Asia Command |
| SEACOORD | Southeast Asia Coordinating Committee |
| SEACOORD | Southeast Asia Coordinating Council |
| SEACORDS | Secure Voice Cordboards |
| SEAITACS | Southeast Asia Integrated Tactical Air Control System |
| SEAL | Sea, Air, and Land |
| SEALORDS | Southeast Asia Lake-Ocean-River Delta Strategy |
| SEAPC | Southeast Asia Pictorial Center |
| SEARA | Southeast Asia Research Associates |
| SEAS | South East Asia Services |
| SEASIA | Southeast Asia |
| SEATO | Southeast Asia Treaty Organization |
| SEAWBS | Southeast Asia Wideband System |
| Sec | Security |
| SECARMY | Secretary of the Army |
| SECDEF | Secretary of Defense |
| SECNAV | Secretary of the Navy |
| SECORD | Secure Voice Cordless Switchboard |
| SECORDS | Secure Voice Cordboards |
| SECSTATE | Secretary of State |
| Section | Navy term for a tactical element of two or more aircraft (usually two)/an Air Force term for two flights of four. |
| SEER | System for Evaluating the Effectiveness of RVNAF |
| Sep/SEP | Separate |
| SEP | Surrendered Enemy Personnel |
| SEPLS | Saigon Electric Power Loop System |
| SERE | Survival, Evasion, Rescue and Escape Course |
| SES | Special Exploitation Service |
| SEVAC | Secure Voice Access Console |
| SEVENTHFLT | Seventh Fleet/Commander, Seventh Fleet |
| SF | Special Forces |
| SFC | Sergeant First Class |
| SFCP | Shore Fire Control Party |
| SFF | SEATO Field Forces |
| SFG | Special Forces Group |
| SFGA | Special Forces Group, Airborne |
| SGU | Special Guerrilla Unit (Laos) |
| SHEDS | Ship Helicopter Extended Delivery System |
| SHRIKE (AGM-45) | Air-to-Surface radar seeking missile. |
| SI | Special Intelligence |
| SIAF | Small Independent Action Force |
| SICR | Specific Intelligence Collection Requirement |
| SIF | Selective identification feature - electronic device with variable codes for identification. |
| SIGINT | Signal Intelligence |
| SILVER DAWN | Code name for an intelligence collecting aircraft. |
| SIMEX | Secondary Items Map Excess |
| SIMS | Single Integrated Military Telecommunications System |
| SIO | Strategic Intelligence Office |
| SIP | Special Interdiction Points |
| SITS | Single Integrated Telecommunications System |
| SJA | Staff Judge Advocate |
| SJR | Special Joint Report |
| SJS | Secretary Joint Staff |
| SKS | Soviet Semiautomatic Carbine, Simonov |
| SLAB | Side Looking Airborne Radar |
| SLAM | Search, Locate, Annihilate and Monitor |
| SLAM | Seeking, Locating, Annihilating, and Maintaining the Area free of the Enemy. |
| SLAR | Side Looking Airborne Radar |
| SLF | Special Landing Force |
| SLO | Senior Liaison Officer |
| SLR | Side-Looking Radar |
| SLSC | Sector Logistics Support Center. |
| SM | Service/Soldier's Medal |
| SM&DSL | Sector Management and Direct Support Logistic Center |
| SM&DSLC | Sector Management and Direct Support Logistics Center |
| SMA | Senior Marine Adviser |
| SMALC | Sacramento Air Logistics Center |
| SMAMA | Sacramento Air Materiel Area |
| SMAR | Special Mission Airlift Request |
| SMF | Special Mission Force |
| SMH | Service to Military Hospitals (ARC) |
| SMI | Service to Military Installations (ARC) |
| SMIAT | Special Military Intelligence Activities Team |
| SMMV | Spanish Medical Mission, Vietnam |
| SMO | Systems Maintenance Office |
| SMP | Special Munitions Package |
| SMPC | Saigon Market Party Committee |
| SMS | Special Mission Service |
| SMSAD | Special Mission Service Advisory Division |
| SMSGT | Senior Master Sergeant |
| Snap-up | A rapid pullup to establish a climb in order to launch a weapon. |
| SNUD | Stock Number User Directive |
| SO | Stockage Objective |
| SOA | Supervisor of Airlift |
| SOC | Special Operations Center |
| Social Change | Producing primary alterations in the non-material culture such as values, attitudes, institutions and social behavior. |
| Social Cohesion | The quality of the interdependence of component institutions of society. |
| Social Mobility | Absence of strict class lines permitting a person to "move upward" within society. |
| Societal Analysis | The intensive and detailed study of a society to include its component institutions, groups and members to provide a basis for counterinsurgency operations. |
| Society | A complex, interdependent system of institutions. |
| SOFA | Status of Forces Agreement |
| SOG | Studies and Observation Group |
| SOI | Signal Operating Instructions |
| SOIC | Sector Operations and Intelligence Center |
| SOI | Standard Operating Instructions |
| SOP | Standing Operating Procedure(s) |
| SOP | Strategic Objectives Plan |
| SOR | Specific Orders and Requirements |
| SOS | Special Operations Squadron |
| SOW | Statement of Work |
| SP | Self- Propelled |
| SP | Special |
| SP | Specialist |
| SPD | Special Projects Division |
| SPECAT | Special Category |
| SPG | Special Planning Group |
| Split-S maneuver | 180° rotation about the aircraft longitudinal axis followed by 180° change of heading in a vertical plane (half loop starting from top). |
| SPOS | Strong Point Obstacle System |
| Spr | Sapper |
| Spt/SPT | Support |
| SPTD | Supported |
| SQ | Squadron |
| Sqdn/SQDN | Squadron |
| SR | Subregion |
| SRA | Strategic Research and Analysis |
| SRAC | Second Regional Assistance Command |
| SRAG | Second Regional Assistance Group |
| SRAO | Supplemental Recreational Activity Office |
| SRO | Senior Ranking Officer |
| SRR | Straggler Recovery and Replacement |
| SRT | Satellite Repair Team |
| SS | Silver Star |
| SS | Steamship |
| SSAR | Southern Search and Rescue Station |
| SSB | Single Sideband |
| SSG | Special Support Group |
| SSI | Standard Signal Instructions |
| SSN | Nuclear Attack Submarine |
| SSOIC | Subsector Operations and Intelligence Center |
| SSS | Shadow Supply System |
| SSS | Simplified Supply System |
| SSS | Sub-subsector |
| SSSG | Special Supply Support Group |
| SSZ | Special/Specialised Strike Zone |
| ST | Short Ton(s) |
| STAB | Strike Assault Boat |
| STAN | Short Ton (2,000 pounds) |
| STAR | Speed Thru Air Supply |
| STAR | Star Far East Corporation |
| STARCOM | Strategic Army Communications Systen |
| STATEDEPT | Department of State |
| STBY | standby |
| STCAN | From (French designed river Patrol craft) |
| STCP | Sector Tactical Command Post |
| STD | Standard |
| STD | Strategic Technical Directorate |
| STOL | Short Take-Off and Landing |
| STON | Short Tons (2,000 lbs) |
| STPD | Short Tons per day |
| STRATCOM | Strategical Command |
| STRATCOM | US Army Strategic Communications Command |
| STRDC | Son Thon Rural Development Cadre (for Montagnards) |
| STS | Specialty Training Standards |
| STYX | Russian Missile |
| STZ | Special Tactical Zone |
| SUB-TECH SCH | Subsidiary Technical School |
| Subversion | Action, principally clandestine or covert, designed to undermine the military, economic, psychological, morale or political strength of a regime. |
| SUL | Small Unit Leader |
| SUPCOM | Support Command |
| Supply Class - Class I | Rations |
| Supply Class - Class II | Clothing and Equipment |
| Supply Class - Class III | Petroleum, Oil, and Lubricants |
| Supply Class - Class IV | Organisational Equipment and Fortification Material |
| Supply Class - Class V | Ammunition |
| Supply Class - Class VA | Air Munitions |
| SUSREP | Senior United States Representative |
| Svc/SVC | Service |
| SVN | South Vietnam (preferably RVN) |
| SVNLA | South Vietnam National Liberation Army |
| SW | Southwest |
| SWIFT | A 50 foot, 32 knot, Radar Equipped Aluminum Boat. |
| Switchology | A coined word addressing the human engineering considerations of switch arrangements. |
| SYNCOM | Synchronous Communications Satellite |