- e
**1.**a symbol for the electric charge on one electron. Since the charges on other particles in atomic physics are whole-number multiples of this charge, the symbolis often used as a unit of measure. 1*e*is equal to approximately 1.602 176 487 x 10*e*^{-19}coulomb, or 160.217 648 7 zeptocoulombs (zC).**2.**a mathematical unit used as the base of "natural" logarithms and exponentials.The real numberis irrational, which means that its decimal expansion is infinite and non-repeating. To 25 significant digits*e*equals 2.718 281 828 459 045 235 360 287. Of the many properties of this number, the most important is that the rate of change in the function*e*is equal to the value of the function itself: an example of the behavior we call "exponential growth." As a result, the larger the value of this function is, the faster the function grows. The Swiss mathematician Leonard Euler (1707-1783) introduced the symbol*e*^{x}, probably because it is the first letter of the word "exponential." Other mathematicians continued to use the letter in his honor. It is sometimes called the Euler number.*e*

*Dictionary of units of measurement.
2015.*