Enter a number in any form — 0.00045, 4.5e-4 or 4.5 x 10^-4 — and the decimal, scientific, engineering and E-notation versions all appear together with the order of magnitude.
A number written as a coefficient between 1 and 10 multiplied by a power of ten, such as 6.022 × 10²³. It keeps very large and very small numbers readable and makes the number of significant figures explicit.
Engineering notation restricts the exponent to multiples of three, so the coefficient runs from 1 to 999. That lines the exponent up with the SI prefixes, which is why 47,000 ohms is written 47 × 10³ Ω and read as 47 kilohms.
It is the plain-text form calculators and programming languages use, where 6.022e23 means 6.022 × 10²³. The tool shows it alongside the typeset version so you can paste values straight into a spreadsheet or code.