Tonle

Tonle is a Khmer term meaning river or watercourse. It appears in many Cambodian place names, typically referring to rivers or water bodies rather than toponyms independent of water.

The best-known example is Tonlé Sap, also called the Great Lake, a large freshwater lake connected to the Mekong River system. The Tonlé Sap River feeds the lake during the rainy season, and the river's flow reverses in the dry season, sending water back toward the Mekong. This seasonal reversal creates a dynamic floodplain that supports extensive fisheries and biodiversity. The Tonlé Sap Basin is widely recognized for its ecological importance and is designated as a UNESCO Biosphere Reserve.

Another prominent use is Tonlé Bassac, a river that flows through Phnom Penh and connects to the Mekong and Tonlé Sap systems. Names incorporating Tonlé also occur for other waterways and settlements throughout Cambodia.

Etymology: In Khmer, tonlé means "river" or "watercourse." The term is predominantly encountered in Cambodia, where hydrological features shape the landscape and local livelihoods.

In English-language usage, Tonlé is capitalized as part of proper place names rather than as a standalone geographic term. The term's prominence in hydrology and culture reflects Cambodia's reliance on river-fed water systems.