What is genocide?

Someone does not have to kill a group of people to committ genocide;  genocide includes the stipulation of intent--so killing members of a group or creating conditions upon members of the group with the intent that those deaths or conditions indicate the intent to destroy the particularly defined group.

So, for instance, the death of 300,000 people of a national group is not necessarily genocide--genocide exists only if the killings are intended as an end in itself: the destuction of the group.  If the killing are a means to an end, for instance, for the control of land or the gain of political power, then that's not genocide.

If however, a few people are killed or suffer conditions by another that mark the other's intent to kill the group defined by people, then that would be genocide. 

Adopted by Resolution 260 (III) A of the U.N. General Assembly on 9 December 1948.  Entry into force: 12 January 1951.

Article II: In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:

(a) Killing members of the group;
(b) Causing serious bodily or mental harm to members of the group;
(c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
(d) Imposing measures intended to prevent births within the group;
(e) Forcibly transferring children of the group to another group.