| synthesis | síntesis |
| synthesize | sintetizar |
| synthesizer | sintetizador |
| synthetase | sintetasa |
| synthetic | artificial |
| Synthetic aperture | Abertura sintética |
| Synthetic aperture radar | Radar de apertura sintética |
| Synthetic biology | Biología sintética |
| Synthetic element | Elemento sintético |
| Synthetic fibre | Fibra sintética |
| Synthetic language | Lengua flexiva |
| Synthetic languages | Lengua flexiva |
| Synthetic radioisotope | Radioisótopo sintético |
| synthetics | sintéticos |
| Synthpop | Synth pop |
| Syntonic comma | Coma sintónica |
| Syphax | Sifax |
| syphilis | sífilis |
| syphilitic | sifilítico |
| syphon | sifón |
| Syphon Filter | Syphon Filter |
| Syr Darya | Sir Daria |
| Syracusa | Siracusa |
| Syracuse | Siracusa |
| Syracuse Orange | Syracuse University Orange |
| Syreeta Wright | Syreeta Wright |
| Syrena | Sirena |
| Syria | Siria |
| Syria national football team | Selección de fútbol de Siria |
| Syriac Catholic Church | Iglesia Católica Siria |
| Syriac Orthodox Church | Iglesia Ortodoxa Siriana |
| Syrian | sirio |
| Syrian Arab Republic | Siria |
| Syrian Brown Bear | Ursus arctos syriacus |
| Syrian nationalism | Nacionalismo sirio |
| Syriana | Syriana |
| Syringa vulgaris | Syringa vulgaris |
| syringe | jeringa |
| syringomyelia | siringomielia |
| Syrma | Sirmia |
| Syrmaticus | Syrmaticus |
| Syrmia | Sirmia |
| Syro-Malabar Catholic Church | Iglesia Católica Siro-Malabar |
| Syro-Malankara Catholic Church | Iglesia católica siro-malankara |
| Syros | Siros |
| Syrtis Minor | Golfo de Gabes |
| syrup | jarabe |
| sysadmin | administrador de sistemas |
| SYSLINUX | Syslinux |
| Syslog | Syslog |
| sysOp | operador del sistema |
| Syssitia | Sisitia |
| system | método |
| System console | Consola de sistema |
| System dynamics | Dinámica de sistemas |
| System engineering | Planeamiento de proyectos |
| System fault tolerance | Copia en papel |
| System Lord | Señores del Sistema |
| System of a Down | System of a Down |
| System of government | Dieta |
| System of law | Derecho |
| System of linear equations | Sistema lineal de ecuaciones |
| System Restore | Restaurar Sistema |
| Systema | Sistema |
| Systema Naturae | Clasificación científica |
| systematic | metódico |
| Systematic element name | Denominación sistemática de elementos |
| systematically | sistemáticamente |
| systematics | sistemática |
| Systematics - study of multi-term systems | Sistema de clasificación |
| systematization | sistematización |
| systematize | clasificar |
| systemic | sistémico |
| Systemic functional grammar | Gramática sistémico funcional |
| Systemic inflammatory response syndrome | Síndrome de respuesta inflamatoria sistémica |
| Systemic therapy | Terapia sistémica |
| systems analysis | análisis de sistemas |
| systems analyst | analista de sistemas |
| Systems architect | Arquitecto de sistemas |
| Systems biology | Biología de sistemas |
| systems engineering | ingeniería de sistemas |
| Systems science | Ciencia de Sistemas |
| systole | sístole |
| systolic | sistólico |
| SYSTRAN | Systran |
| Syzygium | Syzygium |
| syzygy | sizigia |
| Szarvas | Cervidae |
| Szczecin | Szczecin |
| Szczecin Lagoon | Stettiner Haff |
| Szechuan cuisine | Gastronomía de Sichuan |
| Szeged | Szeged |
| Szegedin | Szeged |
| Szkieletor | Szkieletor |
| Szlachta | Nobleza de Polonia y Lituania |
| Szymon Winawer | Szymon Winawer |
| Széchenyi Chain Bridge | Puente de las Cadenas |
| Székely | Székely |
