A clever way of writing 1 as a fraction in which the numerator is equal to the denominator but the numerator and the denominator have different units. For example, (1,000 m)/(1 km) is a conversion factor because 1,000 m = 1 km. (1 ft)/(12 in) is a conversion factor because 1 ft = 12 in.
A term used to connote how accurate a measurement is. The more significant digits in a measurement, the more precise that measurement is.
A number written as a product of a single digit and a power of 10.
The number of digits after the given number has been put into scientific notation. The number of digits that are known in a measurement, plus one digit that is estimated.