It is said to derive from the Khmer word ‘nakorn’ or from the Sanskrit 'nagara’, which bear the same meaning.
The term 'Angkor' refers variously to:
the Angkor Empire;
the Angkor Era, the five century period of the reign of the Angkor kings, from the coronation of Jayavarman II in 802 CE until the last Angkor temples were built in 1295, though Angkor Thom would remain the capital of the kingdom until 1431 or 1432;
the Angkor temples built during the reign of the Angkor kings throughout Southeast Asia, but especially those found in today's Angkor Archaeological Park near Siem Reap, Cambodia.
The Angkor Empire (Khmer: អាណាចក្រអង្គរ: Anachak Angkor), also known as the Khmer Empire (Khmer: ចក្រភពខ្មែរ: Chakrphup Khmer or អាណាចក្រខ្មែរ Anachak Khmer), was the predecessor state to modern Cambodia ("Kampuchea" or "Srok Khmer" to the Khmer people).
Angkor was a Hindu-Buddhist empire in Southeast Asia. It was founded in 802 by Jayavarman II, who established its first capital at Hariharalaya (modern day Roluos), and ended with the fall of Angkor Thom as its capital in 1432.
The Angkor empire grew out of the former kingdoms of Funan and Chenla, and at times it ruled over and/or vassalised most of mainland Southeast Asia and parts of Southern China, stretching from the tip of the Indochinese Peninsula northward to modern Yunnan province, China, and from Vietnam westward to Myanmar.