Apart from being the most frequent letter in, for example, English, French, Spanish, Italian, German and (especially) Dutch, in some languages e can constitute a whole word.
In Italian, Portuguese, Spanish e a number of other Romance languages, e is a common conjunction meaning “and”. In Welsh and Scottish Gaelic, e is a pronoun for “he” or “him”. In Hungarian, this word means “this”.
The irrational number e (2.71828...) is a mathematical constant, the base of the natural logarithm. In physics, e is a fundamental constant known as the elementary charge. Also, e is a symbol for the electron, sometimes written as e− to avoid confusion with the positron, e+. In astronomy, e denotes orbital eccentricity, a parameter that determines the amount by which an object’s orbit deviates from a perfect circle. Finally, ℮ or the estimated sign is a mark that you can see on many pre-packed goods (such as chocolate bars and bottles of drink) sold in the EU.