| Abbreviation | Definition |
|---|---|
| H | Hot |
| HAADF | high-angle annular dark field SEM |
| HAARP | Hf Active Auroral Research Program (Hf being "high frequency") |
| HAI | Horizontal Advance Increment |
| HAM | Hoshino Anniversary Model |
| HARPS | High Accuracy Radial velocity Planet Searcher (spectrography) |
| HB | Hot Bands |
| HB | Hydrogen Bonding |
| HBT | Hanbury Brown-Twiss |
| HC | Hard Condition |
| HC | Heteroclinic Connection |
| HCL | Harvard Cyclotron Laboratory |
| HCP | hexagonally close-packed |
| HD | heavy density |
| HDOP | Horizontal Dilution Of Position |
| HDT | Heat Distortion Temperature |
| HE | high energy |
| HEA | High Energy Astrophysics |
| HEAD | High Energy Astrophysics Division |
| HEBT | High-Energy Beam Transport |