| symptomatic | sintomático |
| symptomatology | semiología |
| Syn addition | Adición anti |
| Syn and Anti addition | Adición anti |
| synagogue | sinagoga |
| Synagogue of El Transito | Sinagoga del Tránsito |
| synalepha | sinalefa |
| Synapomorphy | Sinapomorfia |
| synapse | sinapsis |
| Synapsida | Mammalia |
| Synaptic Package Manager | Synaptic |
| Synaptic plasticity | Neuroplasticidad |
| Synaptic vesicle | Vesícula sináptica |
| Synarchism | Sinarquía |
| Syncarpha | Heliopsis |
| synch | sincronizar |
| synchrocyclotron | sincrociclotrón |
| synchromesh | cambio sincronizado |
| synchronised swimming | nado sincronizado |
| synchronization | sincronización |
| synchronize | sincronizar |
| Synchronized Multimedia Integration Language | SMIL |
| synchronous | sincrónico |
| Synchronous optical networking | SONET |
| Synchronous rotation | Rotación síncrona |
| synchrotron | sincrotrón |
| Synchrotron radiation | Radiación sincrotron |
| syncopate | sincopar |
| syncopation | síncopa |
| syncope | síncopa |
| syndesmosis | sindesmosis |
| syndical | sindical |
| syndicalism | sindicalismo |
| syndicalist | sindicalista |
| syndicate | sindicato |
| syndrome | síndrome |
| synecdoche | sinécdoque |
| synecology | sinecología |
| synergistic | sinergético |
| Synesius | Sinesio de Cirene |
| Synesthesia | Sinestesia |
| Syngman Rhee | Syngman Rhee |
| Syngnathidae | Syngnathidae |
| Syngnathiformes | Syngnathiformes |
| synod | sínodo |
| Synod of Elvira | Concilio de Elvira |
| Synod of Hippo | Concilio de Hipona |
| Synodic period | Período orbital |
| synonym | sinónimo |
| Synonymical | Sinónimo |
| synonymous | sinónimo |
| synopsis | resumen |
| Synoptic chart | Carta meteorológica |
| Synoptic problem | Problema sinóptico |
| Synoptic scale meteorology | Escala sinóptica |
| synovitis | sinovitis |
| synovium | sinovia |
| syntactic | sintáctico |
| Syntactic stylistics | Sintaxis |
| Syntagma Square | Plaza Sintagma |
| syntax | sintaxis |
| Syntax of programming languages | Sintaxis |
| Synth | Sintetizador |
| Synth pad | Po |
| 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 |
