| Arc of contact (wrap angle) θ | The angle over which the belt touches a pulley. Matters on the small pulley; below 180° reduces capacity (factor Kα). |
| Banded belt | Several V-belts joined by a tie band, for shock loads and to stop turnover. |
| Bottoming | A belt touching the bottom of the groove: worn groove or wrong section. Causes slip. |
| Centre distance C | Distance between the two shaft centres. |
| Cogged / notched | Belt with notches on the underside so it bends easily round small pulleys and runs cooler. |
| Datum diameter / datum length | The reference diameter of the pulley and the matching length of the belt, at the datum line. Used for all calculations on ISO-system belts. |
| Datum width | Width of the groove (and belt) at the datum line: 8.5, 11, 14, 19 mm for Z/SPZ, A/SPA, B/SPB, C/SPC. |
| Deflection force | The force needed to push a belt sideways by 1/64 of its span; used to set and check tension. |
| Design power Pd | Motor power × service factor. |
| Driver / driven | The pulley on the motor / the pulley on the machine. |
| Effective length | Length at the outside of the belt (RMA narrow belts, poly-V). |
| Effective pull Te | The tension difference (tight minus slack side) that transmits the power: Te = 1000 P / v. |
| Groove angle β | The included angle of the pulley groove, about 32–38° depending on section and diameter. |
| Idler | A free-running pulley used to take up slack or increase arc of contact. |
| Kα (arc correction factor) | Reduces belt rating for arcs below 180°. |
| KL (length factor) | Adjusts belt rating for belt length. |
| Matched set | Belts made or selected to the same length tolerance so they share load in a multi-belt drive. |
| Pitch (timing belts) | Distance between tooth centres, e.g. 8 mm for HTD 8M. |
| Raw-edge | Belt with cut, uncovered sides for higher grip. |
| Rim speed | Peripheral speed of a pulley: limits apply to cast iron (≈ 30 m/s). |
| Service factor | Multiplier for shock, starting torque and running hours. |
| Slip | The small speed loss of a V-belt (≈ 1–2 %); excessive slip causes heat and wear. |
| Span length | The free length of belt between the pulleys' tangent points. |
| Static (installation) tension | Belt tension at rest, set at installation. |
| Synchronous belt | Timing belt: toothed, no slip. |
| Take-up | Adjustment available to tension the belt as it beds in and stretches. |
| Taper-lock bush | Split tapered bush that locks a pulley to a shaft; changing the bush changes the bore. |
| Teeth in mesh | Number of timing belt teeth engaged on the small pulley; keep ≥ 6. |
| Tight side / slack side | The span being pulled by the driver / the returning span. |
| Turnover | A V-belt rolling over in its groove. |
| VSD / VFD | Variable-speed (frequency) drive controlling the motor speed. |
| Wedge belt | Narrow V-belt (SPZ–SPC, 3V/5V/8V) with higher power per belt. |