| Arch | Archaerhodopsin 3 from Halorubrum sodomense |
| FRET | Förster resonance energy transfer |
| GECI | Genetically encoded calcium indicator |
| GEVI | Genetically encoded voltage indicator |
| PRSB | Protonated retinal Schiff base |
| QuasAr | Quality superior to Arch |
| Ret_xxx | Retinal with absorption maximum approximately at xxx nm |
| RSB | Retinal Schiff base |
| Trp | Tryptophan |
| Tyr | Tyrosine |
| VSD | Voltage sensing domain |