- Cloning
- Cloning vectors
- Clopen
- Clopyralid
- Closed
- Closed convex function
- Closed head injury
- Closed systems
- Closed-cycle gas turbine
- Closed-form expression
- Closed-head injury
- Closed-loop
- Closed-loop control
- Closed-loop controller
- Closed-loop manufacturing
- Closed-loop pole
- Closed-loop recycling
- Closed-loop transfer function
- Closeness
- Closeness centrality
- Clostridia
- Clostridiaceae
- Clostridium acetobutylicum
- Clostridium autoethanogenum
- Clostridium beijerinckii
- Clostridium botulinum
- Clostridium difficile
- Clostridium ljungdahlii
- Clostridium pasteurianum
- Clostridium perfringens
- Clostridium saccharobutylicum
- Clostridium sporogenes
- Clostridium tetani
- Clostridium thermocellum
- Closure
- Closure operator
- Closure phase
- Cloth face mask
- Cloth filters
- Cloth modeling
- Cloth of gold
- Clothes dryer
- Clothianidin
- Clothing industry
- Clothtech
- Cloud
- Cloud chamber
- Cloud computing
- Cloud computing architecture
- Cloud computing security
- Cloud condensation nuclei
- Cloud database
- Cloud manufacturing
- Cloud point
- Cloud radiative forcing
- Cloud robotics
- Cloud security
- Cloud seeding
- Cloud storage
- Cloud storage service
- Cloud-native
- CloudCompare
- Cloudant
- Cloudlet
- Clover
- Clozapine
- Cls
- Cluster analysis
- Cluster graph
- Cluster headaches
- Cluster manager
- Cluster of differentiation
- Cluster sampling
- Clustering coefficient
- Clusters
- Clutch
- Clutter
- Cmh2o
- Cnoidal waves
- Co-adaptation
- Co-carcinogen
- Co-channel interference
- Co-energy
- Co-fermentation
- Co-fired ceramic
- Co-firing
- Co-location
- Co-occurrence networks
- Co-oximeter
- Co-processing
- Co-receptor
- Co-simulation
- Co-stimulation
- Co-training
- Co3O4
- CoAP
- Coacervates
- Coactivators
- Coagulase
- Coagulation
- Coagulopathy
- Coal
- Coal analysis
- Coal basin
- Coal blending
- Coal combustion products
- Coal combustion residuals
- Coal dust
- Coal gas
- Coal gasification
- Coal measures
- Coal mining
- Coal oil
- Coal phase-out
- Coal preparation plant
- Coal refuse
- Coal slurry
- Coal slurry pipeline
- Coal tar
- Coal-fired power stations
- Coal-mining region
- Coalbed methane
- Coalescence
- Coalescer
- Coaling
- Coarctation of the aorta
- Coarea formula
- Coarse bubble diffusers
- Coarse structure
- Coarse-grained
- Coastal engineering
- Coastal erosion
- Coastal flooding
- Coastal management
- Coastal morphodynamics
- Coastal plains
- Coastal reservoirs
- Coastal sediment transport
- Coastline paradox
- Coated fabrics
- Coated paper
- Coating
- Coaxial
- Coaxial cable
- Coaxial rotor
- Cob
- Cobalt
- Cobalt acetate
- Cobalt blue
- Cobalt ferrite