死亡 (sǐ wáng) is the formal, neutral word for death. 死 means to die (also used colloquially: 我饿死了, I'm starving) and 亡 means to perish or be lost. Together they form the literary and official term used in medical, legal, and formal contexts. In everyday speech 死 alone or 去世 (qù shì, to pass away, respectful) are more common. 死亡率 (death rate) and 死亡原因 (cause of death) are common compounds.