- Classical antiquity
- Classified
- Clatter
- Clause
- Claustrophobic
- Clavicle
- Clay
- Clean down
- Clean from
- Clean hands
- Clean-handed
- Clean-shaven
- Cleanliness
- Cleanness
- Cleverness
- Cliff
- Climbers
- Climbing plant
- Climbing stem
- Clinging
- Clinging steadfastedly on
- Clinical psychology
- Clink
- Clip
- Clippers
- Clipping
- Clitoria
- Cloakroom
- Clockwork
- Clod
- Clod hopper
- Cloister
- Clop
- Close around
- Close down
- Clouds
- Clove
- Cloven
- Clownish
- Cloze test
- Club
- Cluck
- Clueless
- Clumsily
- Clumsy
- Clunker
- Clutter
- Coals
- Coals to new castle
- Coast
- Coat of arms
- Coated
- Coattails effect
- Cobalt bomb
- Cobble
- Cobbler
- Cobol
- Cobra
- Cocaine
- Cock
- Codex
- Codger
- Coed
- Coefficient
- Coessential
- Coffee break
- Coffee plant
- Coffer
- Cogitate
- Cogitation
- Cogitative
- Cognate
- Cognisance
- Cold storage
- Cold war
- Cold-blooded
- Cold-hearted
- Coleslaw
- Coliform
- Coliseum
- Colitis
- Collaboratively
- Collage
- Collapse
- Collapsible
- Collar beam
- Collectedly
- Collective noun
- College
- Collegian
- Colliding
- Collision
- Collision course
- Collusiveness
- Collyrium
- Colocasia
- Comb
- Combative
- Combing
- Come