Nomenclature
| Latin | Definition | Unit |
| a | Local speed of sound | m/s, ft/s |
| a | Semimajor axis of inlet elliptic lip (internal) | m, ft |
| a | Swirl profile parameter | — |
| at | Speed sound based on total temperature | m/s, ft/s |
| A | Area | m2, ft2 |
| An | Projection of area in the normal direction | m2, ft2 |
| A9 | Nozzle exit flow area | m2, ft2 |
| Aref | Reference area | m2, ft2 |
| Ao | Inlet (freestream) capture area | m2, ft2 |
| A1 | Inlet capture area | m2, ft2 |
| A8, A8geo | Nozzle throat area (geometrical area) | m2, ft2 |
| A8eff | Effective nozzle throat area | m2, ft2 |
| AB | Blocked area (due to boundary layer) | m2, ft2 |
| Ab | Burning area of grain in solid rocket motors | m2, ft2 |
| AE | Effective area | m2, ft2 |
| AHL | Inlet highlight area | m2, ft2 |
| AM | Maximum nacelle area | m2, ft2 |
| Ath | Inlet throat area | m2, ft2 |
| A* | Sonic throat, choked area | m2, ft2 |
| b | Semiminor axis of inlet elliptic lip (internal) | m, ft |
| b | Swirl profile parameter | — |
| B | Blockage | — |
| B | Compressor instability parameter due to Greitzer | — |
 |
Absolute velocity vector in turbomachinery | m/s, ft/s |
| C | Absolute flow speed, i.e.,  |
m/s, ft/s |
| c | Chord length | m, ft |
| c | Effective exhaust velocity in rockets | m/s, ft/s |
| c* | Characteristic velocity in rockets | m/s, ft/s |
| Cr, Cθ, Cz | Radial, tangential, axial velocity components in the absolute frame of reference | m/s, ft/s |
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