- cylindrical lens
- cylindrical level
- cylindrical lock
- cylindrical mouthpiece
- cylindrical pin
- cylindrical pinch
- cylindrical reflector
- cylindrical shell
- cylindrical surface
- cylindrical valve
- cylindrical vault
- cylindrical wave
- cylindrical waveguide
- cylindrical winding
- cyllosis
- cymometer
- cymomotive force
- cypher
- cypherpunks
- cypridopathy
- cystadenoma
- cystic calculus
- cystolithiasis
- D bus
- D indicator
- D scan
- D-channel
- D-region
- dab
- dabber
- dabble
- dacron
- dacryagogic
- dacryocystis
- dacryogenic
- dacryosyrinx
- daddy
- dado
- daemon
- daily
- daily amplitude
- daily capacity
- daily discharge
- daily dose
- daily flow
- daily newspaper
- daily output
- daily production
- daily range
- daily salary
- daily wage
- dais
- daisy
- daisywheel
- daisywheel printer
- dale
- dam
- dam abutment
- dam course
- dam crest
- dam face
- dam level
- dam outlet
- dam rupture
- dam-proof
- damage
- damage control
- damage curve
- damage factor
- damageable
- damaged
- Darlington configuration
- Darlington stage
- dash line
- dashed link
- dashpot
- data acquisition
- data aggregate
- data bank
- data bus
- data capture
- data carrier
- data center
- data channel
- data clock
- data communication
- data compaction
- data concentrator
- data directory
- data encryption
- data feeds
- data file
- data flow
- data format
- data generator
- data handling
- data hierarchy
- data independence
- data inscriber
- data language