Final answer:
The Euphrates is the longest river in Southwest Asia and the Tigris is one of the two defining rivers of Mesopotamia.
Step-by-step explanation:
The Euphrates and Tigris Rivers, also known as the Tigris-Euphrates river system, have several distinct characteristics. The Euphrates is the longest river in Southwest Asia, flowing through Syria from Turkey before entering Iraq. It is an important source of water in the Fertile Crescent region. On the other hand, the Tigris is one of the two defining rivers of Mesopotamia. It originates in southeastern Turkey, flows through Iraq, and eventually empties into the Persian Gulf.