| AIP： | Aerodynamic Interface Plane |
| ARP： | Aerospace Recommended Practice |
| C： | Offset term (Equation A9) |
| C(τ)： | Covariance of time varying pressures |
| f： | Frequency |
| KC： | Circumferential distortion sensitivity (Equation A9) |
| KR： | Radial distortion sensitivity (Equation A9) |
| L： | Characteristic length (cowl lip to compressor face) |
| MPR： | Multiple-per-revolution element |
| N： | Number of instrumentation rings |
| P： | Total pressure |
| -
P： | Time-averaged total pressure |
| PAV： | Ring average total pressure |
| PAVLOW： | Average total pressure of low total-pressure region for a ring (Equations A2 and A5) |
| PFAV： | Face average total pressure (A.1.2) |
| PR： | Pressure ratio of given compression components |
| PRDS： | Stability pressure ratio with distortion |
| PRO： | Operating pressure ratio |
| PR1： | Undistorted stability pressure ratio |
| P(θ)： | Total pressure at any angle θ for a given ring |
| Q： | Number of low-pressure regions |
| R： | Radius |
| RMS： | Root mean square |
| SM： | Stability margin |
| T： | Total temperature |
| ΔPC/P： | Circumferential distortion intensity element (Equations A2 and A5, A.1.1) |
| ΔPR/P： | Radial distortion intensity element (Equation A8, A.1.2) |
| ΔPRMS： | Root mean square of time varying total-pressure fluctuations |
| ΔPRS： | Stability pressure ratio loss (Equation A9) |
| ΔSM： | Stability margin loss (Equation A10) |
| θ： | Circumferential location in degrees |
| θ
+： | Extent of high-total-pressure region |
| θ
–： | Extent of low-total-pressure region |
| τ： | Time increment |
| φ (f)： | Power spectral density of time-varying pressure |
| c： | Circumferential |
| i： | |
| j： | |
| k： | |
| MAX： | |
| MIN： | |
| r： | |