is it an island?
No, it is a marginal sea.
South China Sea
is a marginal sea 
neighboring countries of the philippines group to the west South China Sea describe its location? It is a marginal sea of the Western Pacific Ocean.
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South China Sea [SEP] Introduction
The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Philippines (mainly Luzon, Mindoro and Palawan), and in the south by Borneo, eastern Sumatra and the Bangka Belitung Islands, encompassing an area of around . It communicates with the East China Sea via the Taiwan Strait, the Phillipine Sea via the Luzon Strait, the Sulu Sea via the straits around Palawan (e.g. the Mindoro and Balabac Strait), the Indian Ocean via the Strait of Malacca, and the Java Sea via the Karimata and Bangka Strait.