- Clock rate
- Clock synchronization
- Closed systems
- Cloud chamber
- Cloud computing
- Cloud condensation nuclei
- Cloud storage
- Clutch
- Co-processing
- Coagulation
- Coal combustion products
- Coal gas
- Coal gasification
- Coal mining
- Coal refuse
- Coal tar
- Coated paper
- Coating
- Cob
- Cobalt blue
- Cobalt-chrome
- Cobaltocene
- Cobble
- Cobblestone
- Coccoliths
- Cochlear implant
- Cockpit
- Code for Sustainable Homes
- Coefficient of restitution
- Coercivity
- Cofactors
- Coffee beans
- Cogeneration
- Cognitive load
- Coherence
- Coherent diffraction imaging
- Cohesion
- Coil-globule transition
- Coining
- Coke
- Cold blast
- Cold cathodes
- Cold seeps
- Cold trap
- Cold welding
- Cold working
- Cold-formed steel
- Colemanite
- Collagen
- Collets
- Collision
- Collision avoidance system
- Colloidal silica
- Colloids
- Color blindness
- Color temperature
- Color vision
- Colorectal cancer
- Colorimeters
- Colorimetry
- Columbite
- Columnar jointing
- Coma
- Combustion
- Combustion chamber
- Comets
- Comminution
- Common-ion effect
- Communication system
- Communications satellites
- Commutator
- Comonomer
- Compaction
- Compactors
- Completion
- Complex number
- Composite armor
- Composite laminates
- Composite materials
- Compressed air
- Compressed sensing
- Compressibility
- Compressible flow
- Compression
- Compression molding
- Compressive strength
- Compressive stress
- Compton scattering
- Computational chemistry
- Computational electromagnetics
- Computational science
- Computer hardware
- Computer networks
- Computer simulation
- Computing
- Concentrate
- Concentration cell
- Concrete
- Concrete blocks
- Concrete cone failure
- Concrete cover
- Concrete degradation
- Concrete mixers
- Concrete pavement restoration
- Concrete pump
- Concrete slabs
- Concrete slump test
- Concretions
- Condensation
- Condensation reaction
- Condensed matter physics
- Condenser
- Conductive ink
- Conductive polymers
- Conductivity
- Cones
- Congeners
- Conglomerate
- Congruence
- Conjugate
- Conjugated system
- Connecting rod
- Conservation of energy
- Conservation of mass
- Constipation
- Constitutive equations
- Constructed wetlands
- Construction aggregate
- Construction waste
- Consumables
- Contact angle
- Contact force
- Contact lenses
- Contact mechanics
- Contact process
- Contact resistance
- Container glass
- Containerization
- Containment building
- Continental crust
- Continuity equation
- Continuous casting
- Continuous function
- Continuous production
- Continuous wave
- Continuum mechanics
- Contour lines
- Contra-rotating propellers
- Contraflexure
- Contrails