The term genocide was coined during the Holocaust
It is the third and most serious indictment against Mr Milosevic, who has already been charged with other alleged war crimes in Kosovo and Croatia. It is also a serious test for the International Criminal Tribunal for the Former Yugoslavia.
As defined by the United Nations in 1948, genocide has turned out to be difficult to prove. So far, eight people have been convicted for their role in the Rwandan genocide, one for the war in Bosnia.
But what is genocide and when can it be applied? Some argue that the definition is too narrow and others that the term is devalued by misuse.
UN definition
The term was coined in 1943 by the Jewish-Polish lawyer Raphael Lemkin who combined the Greek word "genos" (race or tribe) with the Latin word "cide" (to kill).
After witnessing the horrors of the Holocaust - in which every member of his family except his brother and himself was killed - Dr Lemkin campaigned to have genocide recognised as a crime under international law.
Article Two of the convention defines genocide as "any of the following acts committed with the intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
The convention also imposes a general duty on states that are signatories to "prevent and to punish" genocide.
Ever since its adoption, the UN treaty has come under fire from different sides, mostly by people frustrated with the difficulty of applying it to different cases.
'Too narrow'
Some analysts argue that the definition is so narrow that none of the mass killings perpetrated since the treaty's adoption would fall under it.
The objections most frequently raised against the treaty include:
But in spite of these criticisms, there are many who say genocide is recognisable.
In his book Rwanda and Genocide in the 20th Century, former secretary-general of Doctors Without Borders, Alain Destexhe says: "Genocide is distinguishable from all other crimes by the motivation behind it.
"Genocide is a crime on a different scale to all other crimes against humanity and implies an intention to completely exterminate the chosen group.
"Genocide is therefore both the gravest and greatest of the crimes against humanity."
Loss of meaning
Mr Destexhe believes the word genocide has fallen victim to "a sort of verbal inflation, in much the same way as happened with the word fascist".
Because of that, he says, the term has progressively lost its initial meaning and is becoming "dangerously commonplace".
Michael Ignatieff, director of the Carr Centre for Human Rights Policy at Harvard University, agrees.
"Those who should use the word genocide never let it slip their mouths. Those who unfortunately do use it, banalise it into a validation of every kind of victimhood," he said in a lecture about Raphael Lemkin last year.
"Slavery for example, is called genocide when - whatever it was, and it was an infamy - it was a system to exploit, rather than to exterminate the living."
The differences over how genocide should be defined, lead also to disagreement on how many genocides actually occurred during the 20th Century.
History of genocide
Some say there was only one genocide in the last century - the Holocaust.
Other experts give a long list of what they consider cases of genocide, including the Soviet man-made famine of Ukraine (1932-33), the Indonesian invasion of East Timor (1975), and the Khmer Rouge killings in Cambodia in the 1970s.
However, some say there have been at least three genocides under the 1948 UN convention:
The first case to put into practice the convention on genocide was that of Jean Paul Akayesu, the Hutu mayor of the Rwandan town of Taba at the time of the killings.
In a landmark ruling, a special international tribunal convicted him of genocide and crimes against humanity on 2 September 1998. Seven other Rwandans have since been convicted of genocide.
Earlier this year, the war crimes tribunal for the former Yugoslavia handed down its first sentence for the crime of genocide, when it found General Radislav Krstic guilty of killing up to 8,000 Bosnian Muslims in Srebrenica.
Two other Bosnian Serbs, General Ratko Mladic and Radovan Karadzic, have also been accused of genocide by the tribunal - both remain at large.
Now, Slobodan Milosevic faces charges of genocide and complicity to commit genocide for alleged crimes in Bosnia during the 1992-1995 war. He is set to go on trial next year.
Mr Milosevic is accused of having "participated in a joint criminal enterprise, the purpose of which was the forcible and permanent removal of the majority of non-Serbs from large areas of the Republic of Bosnia-Hercegovina".
Being the most prominent European to face a war crimes court since the Nuremberg trials of Nazi leaders at the end of World War II, campaigners hope his trial will set an important precedent.