sphere and suspension culture subculturing - (Jan/24/2011 )

What is definded as a "passage" when subculturing sphere and suspension cultures?
is it only changing the medium after centrifugation or is it a singularization of cells (e.g. by enzymes as trypsin for adherent cultures).
Thanks in advance!

Usually it is when you remove 1/3 or more of the population of cells and start them growing again. I don't know about sphere cultures though.