One difference between a bay and a gulf is size: bays are typically smaller than gulfs. A gulf may contain one or several bays, such as the Galveston Bay and Tampa Bay, which form part of the Gulf of Mexico. However, some bays may encompass a bigger area than a gulf, such as the Bay of Bengal, which is larger compared to the Gulf of Aden, Gulf of Tonkin and Gulf of Oman.
Bays and gulfs share many of the same characteristics. Although there are some generally accepted distinctions, for the most part, the differences between bays and gulfs are not well-defined and straightforward. There are instances when the two terms are used interchangeably.
Bays are formed when the land along the coast curves inward to create an indentation or when a small body is separated from the main body of water. Whereas gulfs form an extension of either an ocean or sea, bays are commonly found near lakes. Some major bays include the Hudson Bay, Bay of Fundy and Bay of Biscay.
Gulfs usually have deeper indentations as compared to bays. The formation of gulfs is the result of the movement of the Earth's crustal plates. The largest gulf in the world is the Gulf of Mexico, which extends towards the Atlantic Ocean via the Straits of Florida. Gulfs are often used as commercial routes for trading. Other major gulfs include the Persian Gulf in the Middle East and Gulf of Carpentaria in Australia.