| Equation | Standard Description | Velocity Field Description |
| Klein-Gord equation |
|
|
| Schrödinger equation |
|
if |
| cl./electrom.wave equation |
|
|
| non-rel. pres. equation |
|
|
| rel. pres. equation | none in general |
|
| cl. vac. feq. |
|
|
| rel. vac. feq. |
|
|
| cl. mat. feq. |
|
|
| rel. mat. feq. (free part.) |
|
for |
| pres. en.-mo. |
|
|