Large body of water partially enclosed by land and is larger than a bay

Gulf

Explanation:

The gulf is a large body of water that is enclosed by land on three sides, while being open toward the sea with one side. The bays are smaller units which are part of the gulfs. These bodies of water are usually very exploited because they are excellent for numerous things, be it making ports for trade, tourism, fishing etc. Some of the best known gulfs in the world are the Persian Gulf and the Gulf of Mexico, with the first one having huge importance for the whole world, while the second one is very important for the Americas.

associative property of addition