| NEPER | Non-SI unit expressing the ratio of two currents or voltages, equal to the natural logarithm of the ratio of the two quantities (5) |
| DECIBEL | A unit for comparing two currents, voltages or power levels equal to one tenth of a bel (7) |
| BRAKEHORSEPOWER | Imperial unit expressing the force available at the shaft of an engine (5,10) |
| EULER | Mathematician who popularised notational conventions including i to denote the imaginary unit and e for the base of the natural logarithm (5) |
| FRACTION | Any rational number that can be expressed as the ratio of two integers (8) |
| LEEWAVES | Oscillations in air currents or foliage around east and west (3,5) |
| WINDSOR | Currents or famous family name (7) |
| BIOLOGICALCLOCK | 10 (logarithm of 1 some calculate) in obstruction of factor in jet lag (10,5) |
| RUISLIP | Town in the London Borough of Hillingdon whose two current MPs are Boris Johnson and Nick Hurd |
| LOD | Logarithm of odds (3) |
| SECANT | In trigonometry, the ratio of the hypotenuse of a right-angled triangle to that of the adjacent side; the reciprocal of the cosine (6) |
| MACH | Physicist who established the principles of supersonics and the ratio of the velocity of a body to the speed of sound (4) |
| SINE | In a right-angled triangle, the ratio of the length of the side opposite an angle to the length of the hypotenuse (4) |
| COSECANT | In geometry, the ratio of the length of the hypotenuse in a right-angled triangle to that of the opposite side (8) |
| THERM | Non-SI unit of heat energy equal to approximately 105 megajoules or 25,200 kilocalories (5) |
| GAIN | Factor by which power or voltage is increased by an amplifier, expressed as the ratio of output to input (4) |
| TORR | Named after E. Torricelli, which non-SI unit of pressure is used in the area of high vacuum? (4) |
| EFFICIENCY | A measure of a mechanical system's effectiveness, usually the ratio of the power delivered by a mechanical system to the power supplied to it (10) |
| MACHNUMBER | Parameter designated to the ratio of an aircraft's velocity divided by the speed of sound at that altitude (4,6) |
| MPH | The ratio of the distance traveled (in miles) to the time spent traveling (in hours). |
