A tributary (or confluent/affluent) is a stream or river which flows into a mainstem (or parent) river, and which doesn't flow directly into a sea. In orography, tributaries are ordered from those nearest to the source of the river to those nearest to the mouth of the river. A confluence is where two or more tributaries or rivers flow together. The descriptive means terms right tributary and left tributary always apply from the perspective of looking downstream (in the direction the current i… (More on Tributary)