"Displacement" is the shortest distance from the initial to the final position of a point P.
Applicable units are those of quantitykind:Length
http://en.wikipedia.org/wiki/Displacement_(vector)
"Displacement" is the shortest distance from the initial to the final position of a point P.
$\Delta r = R_f - R_i$, where $R_f$ is the final position and $R_i$ is the initial position.
http://www.iso.org/iso/catalogue_detail?csnumber=43012