What does the ln or 1n mean in this equation?

Question

What does the ln mean here?

It's from this page.

https://en.wikipedia.org/wiki/Universally_unique_identifier#Collisions

Finally, what could I have done to find out for myself? (What did I miss?) I know so little I can even tag the question!

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Just because it might be useful for someone working on database identifiers, here's the code I ended up with.

    public static double HappyBirthday(double charCount, double keyLength = 9)
    {
        // Computes the number of IDs that would need to exist in a set
        // before there's a 50% chance of a collision.

        const double chanceOfCollision = 0.5;
        double spaceLength = Math.Pow(charCount, keyLength);

        var spacesConsumed = Math.Sqrt(2 * spaceLength * Math.Log(1 / (1 - chanceOfCollision)));

        return spacesConsumed;
    }

Answer 1

It is the natural logarithm. It is defined as $$\ln x =\log_e x$$ Where $e$ is the Euler's number, defined as $$e=\sum_{k\geq 0}\frac{1}{k!}=\lim_{n\to\infty}\left(1+\frac{1}{n}\right)^n$$ Sometimes l looks like $1$ in Calibri font.