A base unit is a standard for expressing the measurement of a base quantity within a particular system of units. For example, length is a base quantity in both SI and the English system, but the meter...A base unit is a standard for expressing the measurement of a base quantity within a particular system of units. For example, length is a base quantity in both SI and the English system, but the meter is a base unit in the SI system only. Since each term in the power series involves the argument raised to a different power, the only way that every term in the power series can have the same dimension is if the argument is dimensionless.
