| Citron | Citrullus | Citrullus colocynthis |
| Citrullus lanatus | Citrus | Citrus aurantiifolia |
| Citrus aurantium | Citrus × paradisi | Citrus ×aurantifolia |
| Citrus ×aurantium | Citrus ×bergamia | Citrus ×clementina |
| Citrus ×limon | Citrus ×paradisi | Citrus ×sinensis |
| Citrus ×tangerina | Citrus clementina | Citrus greening disease |
| Citrus japonica | Citrus limettioides | Citrus maxima |
| Citrus medica | Citrus medica var. sarcodactylis | Citrus production |
| Citrus psorosis virus | Citrus reticulata | Citrus reticulata × sinensis |
| Citrus tangerina | Citrus tristeza virus | Cittaslow |
| City | City bicycle | City block |
| City car | City Connection | City designated by government ordinance |
| City Football Group | City Hunter | City life (لعبة) |
| City Life (video game) | City Lights | City Manager |
| City marketing | City network | City of Arts and Sciences |
| City of Ember | City of God (2002 film) | City of Life |
| City of Life and Death | City of London | City of Manchester Stadium |
| City of the Dead (Cairo) | City Point, Wisconsin | City Protocol |
| City Slickers | City University London | City University of New York |
| City wiki | City Year | City-building game |
| City-state | Ciutat de Palma | Civetone |
| CIVETS | Civettictis civetta | Civic intelligence |
| Civic political culture | Civics | Civil and political rights |
| Civil authority | Civil aviation | Civil Aviation Administration of China |
| Civil Aviation Affairs | Civil Aviation and Meteorological Authority of Yemen | Civil Aviation Authority (United Kingdom) |
| Civil code | Civil discourse | Civil disobedience |
| Civil engineering | Civil Guard (Spain) | Civil law (legal system) |
| Civil liberties | Civil registry | Civil rights referendum |
| Civil society | Civil uprising phase of the Syrian Civil War | Civil war in Afghanistan (1989-1992) |
| Civil war in Afghanistan (1989–92) | Civil war in Afghanistan (1992-1996) | Civil war in Afghanistan (1992–96) |
| Civil war in Afghanistan (1996-2001) | Civil war in Afghanistan (1996–2001) | Civil war in Tajikistan |
| Civil-military operations | Civilian | Civilian control of the military |
| Civilisées | Civilization | Civilization (series) |
| Civilization V | Civilization V: Brave New World | Civilized core |
| Civitas Popthensis | Cizre | CJ Parker (wrestler) |
| CJCUC | CKM matrix | Cl |
| Claddagh ring | Cladding (construction) | Cladistics |
| Cladium mariscus | Cladobranchia | Cladocera |
| Cladorhynchus | Cladorhynchus leucocephalus | Cladosporium |
| Cladrastis kentukea | Claflin, Kansas | Claiborne County, Tennessee |
| Claiborne Parish, Louisiana | Claim rights and liberty rights | Claimed moons of Earth |
| Clair Cameron Patterson | Claire City, South Dakota | Claire Danes |
| Claire Etcherelli | Claire Holt | Claire Lee Chennault |
| Claire Redfield | Clairmarais | Clairton, Pennsylvania |
| Clam AntiVirus | Clam Falls, Wisconsin | Clam Lake Township, Michigan |
| Clam Union Township, Michigan | Clamator | Clamator coromandus |
| Clamator glandarius | Clamator jacobinus | ClamAV |
| CLAMP | ClamWin | ClamWin Antivirus |
| Clancy Brown | Clandestine abuse | Clanga clanga |
| Clanga pomarina | Clangula hyemalis | Clans, Alpes-Maritimes |
| Clapper bridge | Clapperboard | Clara Barton |
| Clara Basiana | Clara Bow | Clara City, Minnesota |
| Clara Janés | Clara Khoury | Clara Zetkin |
| Clarabelle Cow | Clarín (Argentine newspaper) | Clare Boothe Luce |
| Clare County, Michigan | Clare, Iowa | Clare, Michigan |
| Clare, New York | Claremont, Illinois | Claremont, Minnesota |
| Claremont, New Hampshire | Claremont, North Carolina | Claremont, South Dakota |
| Claremont, Virginia | Claremore, Oklahoma | Clarence (2014 TV series) |
| Clarence Acuña | Clarence Day | Clarence Goodson |
| Clarence King | Clarence L. Johnson | Clarence Nash |
| Clarence Seedorf | Clarence Township, Michigan | Clarence Williams III |
| Clarence, Iowa | Clarence, New York | Clarendon Hills, Illinois |
| Clarendon Township, Michigan | Clarendon, Arkansas | Clarendon, New York |
| Clarendon, Quebec | Clarendon, Texas | Clarendon, Vermont |
| Clarias batrachus | Clariden | Clariidae |
| CLARINASE | Clarinda, Iowa | Clarinet |
| Clarington, Ohio | Clarion County, Pennsylvania | Clarion, Iowa |
| Clarissa, Minnesota | Clarithromycin | Clark County, Indiana |
| Clark County, Wisconsin | Clark Duke | Clark Gable |
| Clark International Airport | Clark Johnson | Clark L. Hull |
| Clark Township, Michigan | Clark, South Dakota | Clarkdale, Arizona |
| Clarke Carlisle | Clarke County, Alabama | Clarke's three laws |
| Clarkedale, Arkansas | Clarkesville, Georgia | Clarkfield, Minnesota |
| Clarkia amoena | Clarks Grove, Minnesota | Clarks Hill, Indiana |
| Clarks, Nebraska | Clarksburg, Massachusetts | Clarksburg, Ohio |
| Clarksburg, Tennessee | Clarksburg, West Virginia | Clarksdale, Mississippi |
| Clarkson, Kentucky | Clarkson, New York | Clarkston, Georgia |
| Clarkston, Michigan | Clarkston, Utah | Clarkston, Washington |
| Clarkstown, New York | Clarksville City, Texas | Clarksville, Allegany County, New York |
| Clarksville, Arkansas | Clarksville, Indiana | Clarksville, Iowa |
| Clarksville, Michigan | Clarksville, New Hampshire | Clarksville, Ohio |
| Clarksville, Tennessee | Clarksville, Texas | Clarksville, Virginia |
| Clarkton, North Carolina | Clarno, Wisconsin | Clarques |
| Clash of Civilizations | Clash of Clans | Clash of clans |
| Clash of Loyalties | Clash of the Titans (2010 film) | Clasper |
| Class (biology) | Class (computer programming) | Class conflict |
| Class consciousness | Class discrimination | Class in Marxist theory |
| Class struggle | Classes of computers | Classful network |
| Classic car | Classic metal | Classical antiquity |
| Classical architecture | Classical compound | Classical conditioning |
| Classical electromagnetism | Classical electron radius | Classical element |
| Classical liberalism | Classical limit | Classical mechanics |
| Classical order | Classical physics | Classical planet |
| Classicism | Classics | Classification of finite simple groups |
| Classification of mental disorders | Classification society | Classified advertising |
| Classless Inter-Domain Routing | Classroom | Classroom design |
| Clathrate hydrate | Clatonia, Nebraska | Clatskanie, Oregon |
| Claude Adrien Helvétius | Claude Étienne Savary | Claude Bernard |
| Claude Berri | Claude Cahen | Claude Chevalley |
| Claude Cohen-Tannoudji | Claude Dornier | Claude Etienne Savary |
