The tongue of alluvial land lying between two converging rivers, from the Persian "do" (two) and "ab" (water); a recurring landform of the northern plains.
- Literally means "two waters"; a doab is the fertile alluvial land enclosed between two rivers before they join.
- The most famous is the Ganga-Yamuna doab (also called the Antarvedi historically) in western Uttar Pradesh, a rich, intensively farmed and densely populated tract.
- The Punjab plains are classically described as five doabs between the five rivers of the Indus system; for example the Bari Doab lies between the Beas and the Ravi, and the Bist (or Bist-Jalandhar) Doab between the Beas and the Sutlej.
- Doabs are highly fertile because they are made of river-laid alluvium and are well watered, supporting wheat, sugarcane, and other intensive crops.
- The term is a geographical descriptor, not a single named place, so different doabs occur across the northern plains.
The meaning ("two waters"), the Ganga-Yamuna doab, and the Punjab doabs (Bari, Bist, and others between the Indus tributaries) are recurring physiography and place-identification facts.
A doab is the land between two rivers; do not confuse it with a delta (the mouth of a river) or an interfluve in general usage. "Punjab" itself means "five waters", and its plains are divided into doabs between those rivers.
Fertile alluvial land between two converging rivers ("two waters"); the Ganga-Yamuna doab is the classic example, and Punjab is divided into doabs.