Fluidity The reciprocal of viscosity is fluidity, usually symbolized by ? = 1 / ? or F = 1 / ?, depending on the convention used, measured in reciprocal poise (cm·s·g?1), sometimes called the rhe. Fluidity is seldom used in engineering practice. [Wikipedia: https://en.wikipedia.org/wiki/Viscosity] Fluid Mechanics UDUnits ftp://ftp.unidata.ucar.edu/pub/udunits/ ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents.