- direct heating
- direct injection
- direct instruction
- direct join
- direct joint
- direct jump
- direct labor
- direct labour
- direct measurement
- direct observation
- direct path
- direct radial
- direct reading
- direct sampling
- direct scanning
- direct stress
- direct tension
- direct tide
- direct voltage
- direct wave
- direct welding
- direct-viewing
- directed
- directed graph
- directed number
- directing body
- directing force
- directing staff
- direction
- direction angle
- direction beacon
- direction finder
- direction finding
- direction indicator
- direction line
- direction number
- diary
- diatomaceous soil
- diazotype material
- dibhole
- dichlorethylene
- dichotomous
- dichroic
- dichroic lamp
- dichromate
- didymium
- die cushion
- die gap
- die stock
- die tap
- die-forging
- dielectric
- dielectric coefficient
- dielectric current
- dielectric film
- dielectric oil
- dielectric susceptibility
- dies
- dies-stock
- diesel fuel
- diesel hammer
- difference amplifier
- difference note
- differential coil
- differential equation
- differential geometry
- differential pressure
- differential screw
- differential settlement
- differential tone
- differential transformer
- differential winding
- differentiate
- differentiating circuit
- differentiating network
- differentiating transformer
- differentiator
- differentiator circuit
- difficulty
- diffluence
- diffract
- diffraction
- diffraction spectrum
- diffuse
- diffuse light
- diffused junction
- diffused photodevice
- diffuser
- diffuser jet
- diffusing screen
- diffusion block
- diffusion coefficient
- diffusion current
- diffusion flame
- diffusion rate
- digest
- digested sludge
- digester
- digestion
- digestion tank