Although you will deal with many, the most common exponential function you'll encounter is the natural exponential function, written as f( x) = ex. Although the base e looks just as generic as the base a in our definition of exponential function, it is not. The e stands for Euler's number, and represents a standard, commonly known, irrational constant, sort of like π. (Note that “Euler” is pronounced “OIL-er,” not “YOU-ler.”)

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