variable 1 
... variable n This removes the variables indicated and these variables can no longer be referenced. If no other variable is using that object, then the space associated with it is removed.
For example, if ``R'' is a ring, then ``kill R'' will only remove the space associated to ``R'' if there are no variables whose base ring is ``R''. In any case, the name ``R'' is removed and can be used again.
Caveat: inside an interrupted computation (see section 7.4) it is not advisable to kill variables, especially the interrupted computation. Dire and unpleasant things await those who do not heed this warning!