| DA | Distribution apportionment; Domoic acid |
| DAHS | Automated data acquisition and handling system |
| DALY | Disability-adjusted life year |
| Damaged Friable Miscellaneous ACM | Damaged friable miscellaneous asbestos containing material |
| Damaged Friable Surfacing ACM | Damaged friable surfacing asbestos containing material |
| Damaged or Significantly Damaged Thermal System Insulation ACM | Significantly damaged thermal system insulation asbestos containing material |
| DB | Decibel |
| DBE | Disadvantaged business enterprise |
| DBH | Diameter at breast height |
| DBMS | Data base management system |
| DBP | Disinfection by-product; Disinfection byproduct |
| DBS/DISH | Direct broadcast satellite |
| DBSS | DataBase Systems Support |
| D.C. | Direct current |
| DCE Recovery Furnace | Direct contact evaporator recovery furnace |
| DCE Recovery Furnace System | Direct contact evaporator recovery furnace system |
| DCI | Data call-in |
| dCMP | Deoxycytidine monophosphate |
| DCO | Delayed compliance order |
| DDB Depreciation | Double declining balance depreciation |
| D-DBP | Disinfectant-disinfection by-product |
| DDC | Direct digital controls |
| DDE | 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene |
| DDT | 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane; Dichlorodiphenyltrichloroethane |
| DE | Destruction efficiency |
| DE Filtration | Diatomaceous earth filtration |
| DEC System | Direct-shell evacuation control system |
| DED | Data element dictionary |
| Dedicated PAI Process Unit | Dedicated pesticide active ingredient process unit |
| Dedicated PMPU | Dedicated pharmaceutical manufacturing process unit |
| DEET | N,N-Diethylmetatoluamide |
| DEF | Diesel exhaust fluid |
| DEM | Digital elevation model |
| DEN | Diethylnitrosamine |
| Derived 5-Cycle CO2 | Derived 5-Cycle Carbon Dioxide |
| DERs | Data evaluation record |
| DES | Diethylstilbestrol |
| Design Controlled Potential PM Emissions Rate | Design controlled potential particulate matter emissions rate |
| DET | Determination of equivalent treatment |
| Dex | Dexamethasone |
| D/F | Dioxins and furans |
| D-Factor | Leukemia inhibitory factor |
| DFR | Direct final rule |
| DHI | Dairy herd improvement |
| DHIA | Dairy herd improvement association |
| DHIR | Dairy herd improvement registry |
| DHTML | Dynamic HTML |
| DI | Deionize; Direct implementation; Distribution integrity; Drainage intensity |
| DIC | Dissolved inorganic carbon |
| Di-EG | Diethylene glycol |
| DIFF | Dry injection fabric filter |
| DIN | Dissolved inorganic nitrogen |
| Direct PM 2.5 Emission | Direct particulate matter 2.5 emission |
| DISPOSITION | RECORDS DISPOSITION |
| DL | Detection limit |
| DLG | Digital line graph |
| DLS/FF | Dry Lime Scrubber/Fabric Filter |
| DMA | Designated management agency |
| DMBA | 7,12-Dimethylbenzanthracene |
| DME | Disturbance monitoring equipment |
| DMR | Discharge monitoring report |
| DMSCC | Direct microscopic somatic cell count |
| DNA | Deoxyribonucleic acid |
| dnapl | Dense non-aqueous phase liquid; Dense nonaqueous phase liquid |
| DNAPLs | Dense non-aqueous phase liquid |
| DNFB | Dinitrofluorobenzene |
| DNS Server | Domain name service server |
| DO | Dissolved oxygen |
| DOC | Dissolved organic carbon |
| DOC (Waste) | Degradable organic carbon |
| DOD | Department of Defense |
| DOE | United States Department of Energy |
| DOI | Digital object identifier |
| DOM | Dissolved organic matter |
| DON | Deoxynivalenol; Dissolved organic nitrogen |
| DOP | Di-sec-Octyl Phthalate; Dissolved organic phosphorus |
| DOP File | Defined organic parent file |
| DOS | Denial of service |
| DOT | Department of Transportation |
| DP | Data processing; Designated person |
| DPD | N,N-Diethyl-p-Phenylene-Diamine |
| DPE | Dual-phase extraction |
| DPI | Dots-per-inch |
| DPM | Diesel particulate matter |
| DPS | Double page spread |
| DPSIR | Driving Force, Pressure, State, Impact, Response |
| DQA | Data quality assessment |
| DQI | Data quality indicator |
| DQIs | Data quality indicator |
| DQO | Data quality objective |
| DQO Approach | Data quality objective approach |
| DQO Process | Data quality objectives process |
| DQOs | Data quality objective |
| DR | Dilution ratio |
| DRE | Destruction and removal efficiency |
| DRI | Direct-reduced iron |
| DRP | Disaster recovery plan; Dissolved reactive phosphorus |
| Drum Reclamation Unit | Waste combustion system |
| Dry ESP System | Dry electrostatic precipitator system |
| Dry FGD Technology | Dry flue gas desulfurization technology |
| DSA | Dry limestone adsorber |
| DSCR | Debt service coverage ratio |
| DSD | Dark-spots disease |
| DSI | Dry sorbent injection |
| DSI System | Dry sorbent injection system |
| DSO | Differing scientific opinion |
| DSP | Decision support platform |
| DSS | Decision support system; Distributed systems support |
| DSSTox | Distributed structure-searchable toxicity database network |
| DST | Drill steam test |
| DTH | Delayed-type hypersensitivity |
| DTV | Digital television |
| DU | Depleted uranium; Dobson unit |
| DUNS | Data universal numbering system |
| DUP | Duplicate |
| DURC | Dual use research of concern |
| DVD | Digital video disc |
| DVT | Deep vein thrombosis |
| DW | Drinking Water |
| DWEL | Drinking water equivalent level |
| DWF | Dry-weather flow |
| DWH | Deepwater Horizon oil spill |
| DWS | Drinking water standards |
| DWSRF Program | Drinking Water State Revolving Fund program |
| DX RIN | DX renewable identification number |
| DYNHYD4 | Hydrodynamic model |
| DYS | Dysrhythmia |