- Diagonal
- Diagonal relationship
- Diamagnetism
- Diammonium phosphate
- Diamond
- Diamond blades
- Diamond cubic
- Diapers
- Diaphragm
- Diaphragm pumps
- Diarrhea
- Diaspore
- Diathermy
- Diatomaceous earth
- Diatomic molecules
- Diazo
- Diazotrophs
- Diborane
- Dicalcium phosphate
- Dicarboxylic acids
- Dichloramine
- Dichlorobenzene
- Dichlorodifluoromethane
- Dichloromethane
- Die
- Die casting
- Dielectric
- Dielectric loss
- Dielectric spectroscopy
- Dielectric strength
- Diels-Alder reaction
- Diesel fuel
- Diethyl ether
- Diethylene glycol
- Diethylzinc
- Differential centrifugation
- Differential equation
- Differential geometry
- Diffraction
- Diffuse reflection
- Diffuser
- Diffusion MRI
- Diffusion pumps
- Diffusionless transformation
- Difluorocarbene
- Digenite
- Digestive enzymes
- Digging
- Digital cameras
- Digital data
- Dihedral
- Diisopropyl ether
- Dikes
- Dilatant
- Dimension stone
- Dimensional analysis
- Dimensionless quantity
- Dimerization
- Dimethoxyethane
- Dimethyl disulfide
- Dimethyl ether
- Dimethyl sulfide
- Dimethyl sulfoxide
- Dimethylamine
- Dimethylformamide
- Dinitrogen pentoxide
- Dinitrogen tetroxide
- Diode
- Diols
- Diorite
- Diphenyl ether
- Dipole
- Dipole antenna
- Dirac equation
- Direct and indirect band gaps
- Direct reduction
- Direct shear test
- Direct stiffness method
- Direct-drive mechanism
- Direction finding
- Directional solidification
- Disaccharides
- Disaster recovery
- Discharge
- Discriminant
- Diseases
- Disinfectants
- Disinfection by-products
- Disk
- Dislocations
- Dispersants
- Dispersion
- Dispersity
- Displacement
- Display device
- Dissipation
- Dissipation factor
- Distal convoluted tubule
- Distillation
- Distribution transformer
- Disulfide
- Ditches
- Dithiocarbamates
- Diuresis
- Diuretics
- Diversion dam
- Dolomite
- Dolomitization
- Door handle
- Dopamine transporter
- Doping
- Dosimeters
- Dosimetry
- Dot product
- Dota-tate
- Double bond
- Double layer
- Double salts
- Double tees
- Double-slit experiment
- Downcycling
- Downforce
- Drag
- Drag coefficient
- Dragon kiln
- Drain
- Drainage
- Drainage basin
- Drainage divide
- Dredging
- Drift velocity
- Drill
- Drill bit
- Drilling
- Drilling and blasting
- Drilling fluid
- Drilling fluid invasion
- Drilling rigs
- Drinking fountains
- Drive shaft
- Dross
- Drug carriers
- Drug overdose
- Drug packaging
- Druses
- Dry cell
- Dry cleaning
- Dry distillation
- Dry lake
- Dry stone