| 5-Hydroxytryptamin | 5-hydroxytryptamine |
| Hydrodynamik | hydrodynamics |
| Hydroxygruppe | hydroxy hydroxyl group |
| 4-Hydroxybutansäure | gamma-hydroxybutyric acid |
| Hydrocortison | hydrocortisone |
| Hydrographie | hydrography |
| Hydroforming | hydroforming |
| Hydrokortison | hydrocortisone |
| Hydronymie | hydronymy |
| Hydrotherapie | hydrotherapy |
| Hydrocephalus | hydrocephalus |
| Hydrochemie | hydrochemistry |
| Hydroenergie | hydropower |
| Hydrogeochemie | hydrogeochemistry |
| Hydrologin | hydrologist |
| Hydrosphäre | hydrosphere |
| Hydroxyl | hydroxyl |
| Hydrozephalus | hydrocephalus |
| Hydrochorie | hydrochory |
| Hydronym | hydronym |