Kill

kill -- surprise -- kills processes. You must supply a pid. If you want to kill a process by name, look at pkill or killall.

kill by itself will cause a process to try to finish what it's doing and save it's state before actually stopping the process, if you pass it the -9 option it will instead kill a process immediately and without waiting or saving any state/information. The HUP flag will cause the process to re-read it's configuration file (basically a restarting of the process).

See also skill