Key figures follow on the conflict that began with peaceful protests for reform but escalated into an all-out civil war drawing foreign jihadists after a brutal crackdown on dissent.
- Casualties -
The Syrian Observatory for Human Rights, which relies on a large network of activists and medics across the country, says that 210,060 people were killed between March 2011 and February 2015.
They included 65,146 civilians, of whom 10,664 were children.
Among the anti-regime fighters, 38,325 were Syrian rebels while 24,989 were foreign jihadists.
On the regime side, the dead included 45,385 soldiers, 29,943 militia fighters, 640 members of Lebanon's Hezbollah Shiite movement, and 2,502 Shiite militiamen from other countries.
The Observatory says the toll is probably "much higher" but it is impossible to gather information in certain areas under regime and jihadist control.
It says about 20,000 people have also gone missing in Syria's infamous jails.
Thousands more -- combatants and civilians -- have been taken hostage by groups including the Islamic State jihadist organisation.
- Refugees and displaced -
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According to UN figures, 11.4 million people have fled their homes, of whom nearly four million have left the country.
Nearly 1.2 million have taken refuge in Lebanon -- equivalent to more than a quarter of its population.
The actual figure is probably higher as many Syrians are unregistered.
Roughly 625,000 have taken refuge in Jordan, 245,000 in Iraq and 137,000 in Egypt.
Turkey says it has accepted about two million.
Refugees are mired in poverty, health problems and growing tensions with local communities where they live in makeshift camps and extremely difficult conditions.
Inside Syria, 60 percent of the population of 23 million is poverty-stricken, the UN's Food and Agriculture Organization estimated in September.
Up to 2.4 million children cannot go to school because of insecurity, the UN children's agency says.
- Economic consequences -
Experts say the conflict has set Syria's economy back by three decades, with half of the population unemployed and most of the infrastructure destroyed.
The International Monetary Fund says its gross domestic product has contracted by more than 40 percent.
The war damage bill comes to some $31 billion, according to official statistics. Oil production has dropped by 96 percent.