There are five forms of prana. They have different names according to the bodily functions with which they correspond. These forms of prana are:
  udana-vayu, corresponding to the throat region and the function of speech
  prana-vayu, corresponding to the chest region
  samana-vayu, corresponding to the central region of the body and the function of digestion
  apana-vayu, corresponding to the region of the lower abdomen and the function of elimination
  vyana-vayu, corresponding to the distribution of energy into all areas of the body

Vayu is a sanscrit term meaning air or breath. We will look at two of these forms: prana-vayu and apana-vayu.