Depending on how you count, there are one to five oceans on Earth.
A look at a globe of the world will show that all the ocean water is connected. Tradition, however, has divided up this superocean into the Pacific, Atlantic, Arctic, Antarctic, and Indian oceans.
Sometimes the Pacific Ocean is divided again into the North Pacific and South Pacific oceans, and the same is true for the Atlantic. On the other hand, sometimes the Arctic and Antarctic oceans are spoken of as part of the Atlantic and Atlantic, Pacific, and Indian oceans, respectively.
This can lead to confusion, but since all the waters flow into each other it is difficult to consider them as having hard and fast boundaries. In fact, we commonly refer to “the ocean,” meaning all the oceans together.
And sometimes we use the word “sea” to mean ocean, but we will try not to do so here.