What scientific notation is
Scientific notation writes any number as a coefficient between 1 and 10 multiplied by a power of ten:
value = a × 10n, 1 ≤ |a| < 10
The exponent n counts how many places the decimal point moves. Large numbers have a positive exponent; numbers smaller than 1 have a negative exponent. It's the compact way to handle the very large (Avogadro's number) and very small (a proton's mass).
Worked example
0.00042 in scientific notation:
Move the point: 0.00042 → 4.2, shifting 4 places right.
Exponent: moving right means a negative power: 10−4.
Result: 4.2 × 10⁻⁴.
Engineering notation
Engineering notation is a variant where the exponent is always a multiple of three, matching the metric prefixes (kilo 10³, mega 10⁶, milli 10⁻³, micro 10⁻⁶). So 47,000 is 4.7 × 10⁴ in scientific notation but 47 × 10³ in engineering notation — handy in electronics where it lines up with units.
Tip: the "e" in a value like 6.022e23 is shorthand for "× 10 to the" — it means 6.022 × 10²³. You can type values in that form here.