| Acronym | Meaning |
| TID | Traveling Ionospheric Disturbance |
| GHO | Generalized Hybrid Orbital (ao) |
| IRS | Internal Recognition Subsequence |
| GIAO | Gage-including Atomic Orbital |
| LKKR | Layer Korringa-Kohn-Rostoker (in Interface Electronic Structures) |
| NVDOC | Non-volatile Dissolved Organic Carbon |
| EQO | Environmental Quality Objective |
| DEIA | DNA Enzyme Immunoassay |
| USEPA | United States Environmental Protection Agency |
| APH | Adiabatically Adjusting |