vedeliku- või gaasivoo mingi elemendi asendi ja aja vektorväli, vector field, which gives the velocity of an element of fluid or gas at a position and time, vookiirus gaasivoo korral on gaasivoo mingi elemendi asendi ja aja vektor, flow velocity u of a fluid is a vector field u = u(x,t), which gives the velocity of an element of fluid at a position x and time t