Stigma (letter) Stigma (letter) Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also used as a numeral symbol for the number 6. In this unrelated function, it is a continuation of the old letter digamma (originally Ϝ, cursive form ), which had served as a numeral since antiquity and was conflated with the σ-τ ligature in the minuscule handwriting of the Middle Ages. The στ ligature (, ) was one of many ligature forms that came into widespread use as
Torque to a vector, whereas for energy, it is assigned to a scalar. A conversion factor may be necessary when using different units of power or torque. For example, if rotational speed (revolutions per time) is used in place of angular speed (radians per time), we multiply by a factor of 2 radians per revolution. In the following formulas, "P" is power, "τ" is torque, and "ν" (Greek letter nu) is rotational speed. Showing units: Dividing by 60 seconds per minute gives us the following. where rotational speed is in revolutions per minute (rpm). Some people (e.g., American automotive engineers) use