| secede | separarse |
| Secernosaurus | Secernosaurus |
| secession | secesión |
| Sechium | Sechium edule |
| Sechura Fox | Pseudalopex sechurae |
| Sechura Province | Provincia de Sechura |
| seclude | aislarse |
| secluded | remoto |
| seclusion | reclusión |
| second | segundo |
| Second Age | Segunda Edad del Sol |
| Second Anglo-Dutch War | Segunda Guerra Anglo-Holandesa |
| Second Athenian Empire | Segunda Confederación de Atenas |
| Second Balkan War | Segunda Guerra de los Balcanes |
| Second ballot | Segunda vuelta electoral |
| Second Battle of Bull Run | Segunda batalla de Bull Run |
| Second Battle of El Alamein | Segunda Batalla de El Alamein |
| Second Battle of Fallujah | Ocupación de Faluya por Estados Unidos |
| Second Battle of Guararapes | Batalla de los Guararapes |
| Second Battle of Kharkiv | Batallas de Jarkov |
| Second Battle of Kharkov | Batallas de Jarkov |
| Second Battle of the Marne | Batalla del Marne |
| second best | segundo |
| second best quality | de segunda categoría |
| Second Boer War | Guerras de los Bóer |
| Second Book of Enoch | Segundo Libro de Enoc |
| second channel | canal secundario |
| Second Chechen War | Segunda Guerra Chechena |
| Second Congo War | Segunda Guerra del Congo |
| Second Council of Constantinople | Segundo Concilio de Constantinopla |
| Second Council of Lyon | Concilio de Lyon II |
| Second Council of Nicaea | Concilio de Nicea II |
| Second Council of the Lateran | Concilio de Letrán II |
| second cousin | primo segundo |
| Second Crusade | Segunda Cruzada |
| Second dynasty of Egypt | Dinastía II de Egipto |
| Second Epistle of Clement | Segunda epístola de Clemente |
| Second Epistle of John | Segunda epístola de Juan |
| Second Epistle of Peter | Segunda epístola de Pedro |
| Second Epistle to the Corinthians | Segunda epístola a los corintios |
| Second Epistle to the Thessalonians | Segunda epístola a los tesalonicenses |
| Second Epistle to Timothy | Segunda epístola a Timoteo |
| Second finger | Dedo corazón |
| second floor | primer piso |
| Second Foundation | Segunda Fundación |
| Second French Empire | Segundo Imperio Francés |
| second hand | usado |
| second hand buy | ocasión |
| Second Industrial Revolution | Segunda revolución industrial |
| Second Intermediate Period of Egypt | Segundo periodo intermedio de Egipto |
| Second International | Segunda Internacional |
| Second Intifada | Intifada de Al-Aqsa |
| Second Italian War of Independence | Campaña de Italia |
| Second Italo-Abyssinian War | Invasión de Etiopía |
| Second law of thermodynamics | Segunda ley de la termodinámica |
| Second Liberian Civil War | Segunda Guerra Civil Liberiana |
| second lieutenant | subteniente |
| Second Life | Second Life |
| Second Macedonian War | Segunda Guerra Macedónica |
| Second Mexican Empire | Segundo Imperio Mexicano |
| Second Mithridatic War | Segunda Guerra Mitridática |
| Second moment of area | Segundo momento de área |
| second name | apellido |
| second nature | segunda naturaleza |
| Second normal form | Segunda forma normal |
| Second Opium War | Segunda Guerra del Opio |
| Second Polish Republic | Segunda República Polaca |
| Second Punic War | Segunda Guerra Púnica |
| Second Republic | Segunda República |
| Second Rzhev-Sychevka Offensive | Operación Marte |
| Second Sacred War | Guerras sagradas |
| Second Schleswig War | Guerra de los Ducados |
| Second Sino-Japanese War | Segunda Guerra Sino-japonesa |
| Second Spanish Republic | Segunda República Española |
| second stomach | segundo estómago |
| Second Sudanese Civil War | Segunda Guerra Civil Sudanesa |
| Second superstring revolution | Segunda revolución de supercuerdas |
| Second Temple | Segundo templo |
| Second Triumvirate | Segundo Triunvirato |
| Second Vatican Council | Concilio Vaticano II |
| Second video of Osama bin Laden surfaces | Segundo video de Osama bin Laden publicado |
| Second Viennese School | Segunda Escuela de Viena |
| Second World | segundo mundo |
| Second World War | Segunda Guerra Mundial |
| second-best | segundo |
| second-class | de segunda clase |
| Second-countable space | Segundo Axioma de Numerabilidad |
| second-degree | de segundo grado |
| second-degree murder | homicidio de segundo grado |
| second-guess | evaluar |
| second-hand | usado |
| second-hand bookshop | libreria de ocasion |
| second-hand buy | ocasión |
| second-hand smoke | fumador pasivo |
| Second-order cybernetics | Cibernética de segundo orden |
| second-person plural | segunda persona del plural |
| second-person singular | segunda persona del singular |
| second-rate | mediocre |
| secondarily | secundariamente |
| secondary | insignificante |
| secondary channel | canal secundario |
| secondary education | educación secundaria |
| Secondary education in France | Liceos en Francia |
| Secondary metabolite | Metabolito secundario |
| Secondary mirror | Espejo secundario |
| secondary school | escuela superior |
| Secondary sector of economic activity | Sector secundario |
| Secondary sector of industry | Sector secundario |
| secondhand | usado |
| secondhand buy | ocasión |
| secondly | en segundo término |
| secondment | comisión de servicio |
| seconds | sobras |
| Seconds From Disaster | Segundos catastróficos |
| secrecy | secreto |
| secret | secreto |
| secret agent | agente secreto |
| secret code | clave |
| secret documents | documentos secretos |
| secret funds | dinero negro |
| Secret Garden | Secret Garden |
| Secret Gospel of Mark | Evangelio secreto de Marcos |
| secret information | información secreta |
| secret of the heart | secreto del corazón |
| Secret of the Runes | Secrets of the runes |
| Secret passage | Pasaje secreto |
| secret police | policía secreta |
| secret Santa | amigo invisible |
| Secret Squirrel | Inspector Ardilla |
| Secret State Police | Gestapo |
| secret storage | escondite |
| secret store | escondrijo |
| Secret treaty of Dover | Tratado de Dover |
| secret voting | votación secreta |
| Secret Wars | Secret Wars |
