
 Vector (spatial)  Wikipedia, the free encyclopedia 
  A spatial vector is a special case of a tensor and is also analogous to a fourvector in relativity (and is sometimes therefore called a threevector in reference to the three spatial dimensions, although this term also has another meaning for pvectors of differential geometry). 
  Vectors can be contrasted with scalar quantities such as distance, speed, energy, time, temperature, charge, power, work, and mass, which have magnitude, but no direction (they are invariant under coordinate rotations). 
  The length or magnitude or norm of the vector a is denoted by 
 en.wikipedia.org /wiki/Vector_(spatial) (2834 words) 
