When working with numbers that span many orders of magnitude it's very helpful to use some form of scientific notation. At its core, scientific notation expresses a number by breaking it down into a decimal ≥1 and <10 (the "significand" or "mantissa") and an integer representing the order of magnitude (the "exponent"). Traditionally this is written as:

3 × 10⁴

While this communicates the necessary information, it has two main downsides:

• It uses three constant characters ("× 10") to separate the significand and exponent.

• It uses superscript, which doesn't work with some typesetting systems and adds awkwardly large line spacing at the best of times. And is generally lost on cut-and-paste.

Instead, I'm a big fan of e-notation, commonly used in programming and on calculators. This looks like:

3e4

This works everywhere, doesn't mess up your line spacing, and requires half as many characters as writing it the traditional way.

There are a bunch of other variants of e-notation, but I don't like any of them as much:

• 3E4: a shorter separator would be easier to read.
• 3e+4: the + is redundant.
• 3⏨4: neat, but requires unicode and can't be pasted into widely-used programming languages and spreadsheet programs.

One downside of "e" notation is that it comes off as less formal than traditional scientific notation. But unless you need to be read as maximally formal I think it's just better all around.