The normal range of humidity was defined in 1950. Since then, a need has existed for a one-part, full range definition of relative humidity that covers the normal range, and the extended range. This article provides a one-part "real moist air" full range definition. It also provides a full range approximation suitable for the range of  -80°C greater than or equal to t greater than or equal to 40°C and p greater than or equal to 500 kPa (- 112°F greater than or equal to t greater than or equal to 104°F and p greater than or equal to 72.5 psia).