This chapter will begin by signaling the importance of defining suicide. It illustrates two main approaches to the definition of suicide, one which focuses on the deliberate nature of suicide and the other which focuses more narrowly on the intention of the person concerned. Following discussions of the instrumental nature of suicide, and the issue of rational suicide, it is shown why it is held that suicide need not involve self-killing, need not require the presence of a desire to die, nor even the death of the person who suicides. Discussions of problematic cases such as altruistic and coerced suicides are also included.