- Contrast agents
- Control rods
- Control system
- Controlled low strength material
- Convection
- Convective mixing
- Convergent boundary
- Convex optimization
- Conveyor belts
- Conveyor system
- Convulsions
- Coolant
- Cooling
- Cooling bath
- Cooling curve
- Cooling towers
- Cooper pairs
- Cooperite
- Coordinate covalent bond
- Coordinate systems
- Coordinated Universal Time
- Coordination complex
- Coordination geometry
- Coordination number
- Coordination sphere
- Copolymers
- Copper
- Copper conductors
- Copper extraction
- Copper foil
- Copper interconnects
- Copper nitrate
- Copper oxide
- Copper sulfate
- Copper sulfide
- Copper toxicity
- Copper-copper sulfate electrode
- Coprocessor
- Coral sand
- Corbel arch
- Cordless
- Cork
- Corneal
- Corona discharge
- Corona treatment
- Coronary artery disease
- Correlation
- Correlation function
- Corrosion
- Corrosion inhibitors
- Corundum
- Cosmic rays
- Cost-effectiveness analysis
- Cotton mills
- Couette flow
- Coulomb explosion
- Coumarin
- Countersink
- Country rock
- Couples
- Coupling constant
- Covalent bond
- Covalent radius
- Covellite
- Cover meter
- Cowl
- Cowling
- Crack closure
- Crack tip opening displacement
- Cracking
- Crane
- Crankcase
- Crankpin
- Crankshaft
- Cratons
- Cray-2
- Crazing
- Creatinine
- Creep
- Creosote
- Crevice corrosion
- Crimped
- Cristobalite
- Critical heat flux
- Critical mass
- Critical phenomena
- Critical point
- Criticality accident
- Crocodile cracking
- Cross product
- Cross sections
- Cross slope
- Cross-bedding
- Cross-laminated timber
- Cross-linked
- Crosstalk
- Crown ethers
- Crucible steel
- Crushed stone
- Crusher
- Crust
- Cryoablation
- Cryogenic electron microscopy
- Cryogenic fuel
- Cryogenic treatment
- Cryogenics
- Cryopreservation
- Cryopump
- Cryosurgery
- Cryotherapy
- Cryptands
- Cryptocrystalline
- Cryptosporidiosis
- Crystal chemistry
- Crystal growth
- Crystal habit
- Crystal oscillator
- Crystal structure
- Crystal systems
- Crystalline silicon
- Crystallinity
- Crystallites
- Crystallization
- Crystallographic defects
- Crystallography
- Crystals
- Cube
- CubeSats
- Cubic crystal system
- Cubic feet
- Cubic metre
- Cubic yards
- Cubits
- Culverts
- Cupola furnace
- Cuprite
- Cupronickel
- Curie
- Curie temperature
- Curing
- Curium
- Current density
- Current sources
- Curtain coating
- Curtain walls
- Curvature
- Cut and fill
- Cutting fluid
- Cutting tools
- Cuvettes