Is the word Mediterranean a noun?

Yes, "Mediterranean" can be a noun, but it can also be an adjective.

Here's how it works:

As a noun:

* It refers to the Mediterranean Sea: "We sailed across the Mediterranean."

* It can refer to the Mediterranean region: "The Mediterranean climate is known for its hot, dry summers."

As an adjective:

* It describes something relating to the Mediterranean Sea or region: "Mediterranean cuisine is famous for its use of olive oil and fresh herbs."

So, the word "Mediterranean" is both a noun and an adjective depending on how it's used in a sentence.