| Circuncentro | Circumscribed circle |
| circuncidado | circumcised |
| circuncidar | circumcise |
| circuncisión | circumcision |
| circunciso | circumcised |
| circundante | around |
| circundar | include |
| circunferencia | circumference |
| Circunferencia de los nueve puntos | Nine-point circle |
| circunflejo | circumflex |
| circunlocución | circumlocution |
| circunloquio | diffuseness |
| circunnavegación | circumnavigation |
| circunnavegar | circumnavigate |
| circunscribir | circumscribe |
| circunscripción | circumscription |
| circunscripción electoral | electoral district |
| circunspección | circumspection |
| circunspecto | circumspect |
| circunsripcion | restriction |
| circunstancia | condition |
| circunstancia fortuita | incidental circumstance |
| circunstancia incidental | incidental circumstance |
| circunstanciado | complicated |
| circunstancial | circumstantial |
| circunstancialmente | circumstantially |
| circunstancias fuera del alcance de uno | circumstances beyond one's control |
| circunstante | bystander |
| circunvalación | belt |
| circunvención | circumvention |
| circunvenir | circumvent |
| circunvolucion | whorl |
| circunvolución | convolution |
| circón | zircon |
| Cirenaica | Cyrenaica |
| cirenaico | Cyrenian |
| Cirene | Cyrene |
| Ciriaco De Mita | Ciriaco de Mita |
| cirilización | Cyrillization |
| Cirilización del chino mandarín | Cyrillization of Chinese from pinyin |
| Cirilización del japonés | Cyrillization of Japanese |
| Cirilo | Cyril |
| Cirilo de Alejandría | Cyril of Alexandria |
| Cirilo de Jerusalén | Cyril of Jerusalem |
| Cirilo y Metodio | Saints Cyril and Methodius |
| cirio | candle |
| Ciro | Cyrus |
| Ciro el Joven | Cyrus the Younger |
| Ciro Ferrara | Ciro Ferrara |
| Ciro I | Cyrus I of Anshan |
| Ciro II el Grande | Cyrus the Great |
| Cirque du Soleil | Cirque du Soleil |
| cirro | cirrus |
| cirrocúmulo | cirrocumulus |
| cirrosis | cirrhosis |
| Cirrosis hepática | Cirrhosis |
| Cirrus uncinus | Cirrus uncinus cloud |
| Cirsium | Cirsium |
| Cirsium arvense | Cirsium arvense |
| Cirsium eriophorum | Cirsium eriophorum |
| Cirsium oleraceum | Cirsium oleraceum |
| Cirsium palustre | Cirsium palustre |
| Cirsium vulgare | Cirsium vulgare |
| Cirth | Cirth |
| ciruela | plum |
| ciruela claudia | greengage |
| ciruela damascena | damson |
| Ciruela de fraile | Plum |
| ciruela pasa | prune |
| cirugia a los pechos | breast augmentation |
| cirugia a los senos | breast augmentation |
| cirugía | operation |
| cirugía a corazón abierto | open-heart surgery |
| cirugía estética | face-lift |
| Cirugía Oral y Máxilofacial | Oral and maxillofacial surgery |
| Cirugía ortopédica y traumatología | Orthopedic surgery |
| cirugía plástica | face-lift |
| Cirugía refractiva | Refractive surgery |
| cirujana | surgeon |
| cirujana veterinaria | veterinarian |
| cirujano | surgeon |
| cirujano dentista | dental surgeon |
| cirujano veterinario | veterinarian |
| Ciryaher | Hyarmendacil I |
| Ciríaco de Ancona | Ciriaco Pizzicolli |
| cirílico | Cyrillic |
