| cicero | cicero |
| ciceroniano | Ciceronian |
| Cicerón | Cicero |
| Cichorium | Chicory coffee |
| Cichorium intybus | Chicory coffee |
| Cicinnurus | Cicinnurus |
| ciclamato | cyclamate |
| ciclamen | cyclamen |
| ciclamino | cyclamen |
| ciclico | circadian |
| Ciclina | Cyclin |
| ciclismo | cycling |
| Ciclismo urbano | Utility cycling |
| ciclista | biker |
| ciclo | cycle |
| Ciclo Atkinson | Atkinson cycle |
| Ciclo Barroco | The Baroque Cycle |
| ciclo biogeoquímico | biogeochemical cycle |
| ciclo biológico | life cycle |
| Ciclo celular | Cell cycle |
| Ciclo CNO | CNO cycle |
| Ciclo de Born-Haber | Born-Haber cycle |
| Ciclo de Calvin | Calvin cycle |
| Ciclo de canciones | Song cycle |
| Ciclo de candidatos de la FIDE | Candidates Tournament |
| Ciclo de Carnot | Carnot heat engine |
| Ciclo de desarrollo | Software development process |
| Ciclo de Fenian | Fenian Cycle |
| Ciclo de Krebs | Citric acid cycle |
| Ciclo de la urea | Urea cycle |
| Ciclo de las manchas solares | Sunspot cycle |
| Ciclo de Rankine | Rankine cycle |
| Ciclo de Ulster | Ulster Cycle |
| ciclo de vida de producto | product life cycle |
| Ciclo de vida del producto | Product life cycle management |
| ciclo de vida material | material life cycle |
| ciclo del agua | water cycle |
| Ciclo del carbono | Carbon cycle |
| Ciclo del combustible nuclear | Nuclear fuel cycle |
| ciclo del nitrógeno | nitrogen cycle |
| Ciclo del oxígeno | Oxygen cycle |
| Ciclo euleriano | Eulerian path |
| Ciclo hamiltoniano | Hamiltonian path |
| ciclo hidrológico | hydrologic cycle |
| Ciclo metónico | Metonic cycle |
| Ciclo Miller | Miller cycle |
| ciclo nutritivo | nutrient cycle |
| Ciclo sexual femenino | Menstrual cycle |
| Ciclo solar | Sunspot |
| Ciclo supercontinental | Supercontinent cycle |
| Ciclo tebano | Theban Cycle |
| Ciclo termodinámico | Thermodynamic cycle |
| Ciclo troyano | Epic Cycle |
| ciclo- | cyclo- |
| Ciclo-cross | Cyclo-cross |
| cicloalcano | cycloalkane |
| cicloalqueno | cycloalkene |
| Ciclocomputador | Cyclocomputer |
| Ciclocross | Cyclo-cross |
| ciclofilina | cyclophilin |
| ciclogénesis | cyclogenesis |
| ciclohexano | cyclohexane |
| ciclohexanona | cyclohexanone |
| Cicloheximida | Cycloheximide |
| ciclomotor | autocycle |
| ciclones | cyclone |
| ciclopropeno | cyclopropene |
| ciclos biogeoquímicos | biogeochemical cycle |
| ciclosilicato | cyclosilicate |
| Ciclosporina | Ciclosporin |
| ciclotrón | cyclotron |
| Cicloturismo | Bicycle touring |
| Cicládico | Cycladic civilization |
| ciclón | cyclone |
| Ciclón Catarina | Cyclone Catarina |
| Ciclón de media latitud | Extratropical cyclone |
| Ciclón polar | Polar cyclone |
| Ciclón Sidr | Cyclone Sidr |
| Ciclón tropical | Tropical cyclone |
| Ciclón tropical del Atlántico Sur | Cyclone Catarina |
| ciclónico | cyclonic |
| Cicno | Cycnus |
| Cicones | Cicones |
| Ciconia | Stork |
| Ciconia ciconia | White Stork |
| Ciconia episcopus | Woolly-necked Stork |
| Ciconia nigra | Black Stork |
| Ciconiidae | Stork |
| Ciconiiformes | Ciconiiformes |
| CICS | CICS |
| cicuta | hemlock |
| Cicuta virosa | Cicuta virosa |
| Cid Highwind | Cid Highwind |
| CIDR | Classless Inter-Domain Routing |
| cidra | citron |
| cidrayote | cushaw |
| CIE-O | International Classification of Diseases for Oncology |
| ciega | blind woman |
| ciegamente | blindly |
| ciego | blind |
| Cielas de Bitinia | Ziaelas of Bithynia |
| cielo | cell |
| Cielo e infierno | Heaven and Hell |
| Cielo profundo | Deep sky |
| Cielo sobre Berlín | Wings of Desire |
| cielos | golly |
| Cielos abiertos | Open skies |
| Cielos Airlines | Cielos Airlines |
| ciempiés | centipede |
| cien | hundred |
| Cien años de soledad | One Hundred Years of Solitude |
| Cien Días | Hundred Days |
| cien metros cuadrados | hundred square meters |
| cien mil | hundred thousand |
| Cien por cien | Hundred per cent |
| ciencia | science |
| ciencia ambiental | environmental science |
| ciencia aplicada | applied science |
| Ciencia cognitiva | Cognitive science |
| ciencia de la alimentación | food science |
| Ciencia de la Religión | Religious studies |
| ciencia de los materiales | materials science |
| Ciencia de Sistemas | Systems science |
| Ciencia de superficies | Surface science |
| ciencia del folklore | folkloristics |
| Ciencia Divina | Divine Science |
| ciencia ficción | science fiction |
| Ciencia ficción dura | Hard science fiction |
| ciencia ficción no convencional | slipstream |
| ciencia forense | forensic medicine |
| ciencia forestal | forestry |
| Ciencia medieval | Science in the Middle Ages |
| ciencia médica | medical science |
| ciencia natural | natural science |
| Ciencia política | Political science |
| Ciencia Traviesa | Wicked Science |
| ciencias | sciences |
| ciencias aplicadas | applied science |
| ciencias de la atmósfera | atmospheric science |
| Ciencias de la computación | Computer science |
| Ciencias de la comunicación | Communication |
| Ciencias de la Salud | Health science |
| ciencias de la tierra | earth science |
| ciencias de la vida | life science |
| ciencias del comportamiento | behavioural science |
| ciencias del suelo | soil science |
| ciencias exactas | exact science |
| Ciencias formales | Formal science |
| ciencias físicas | physical science |
| ciencias naturales | natural science |
| ciencias políticas | political science |
| ciencias sociales | social science |
| cienciocracia | scientocracy |
| Cienciología | Scientology |
| Cienciometría | Scientometrics |
| cieno | sludge |
| cientificesa | scientist |
| cientificidad | scientificity |
| cientifico | scientific |
| Cientista | Scientist |
| ciento | hundred |
| científica | scientist |
| científicamente | scientifically |
| científice | scientist |
| científico | scientist |
| Científico loco | Mad scientist |
| Científicos crean súper ratones en laboratorio de Estados Unidos | Genetically altered mice are superathletes |
| Científicos disidentes sobre la hipótesis que correlaciona VIH con SIDA | AIDS reappraisal |
