Before I answer the question, I want you to know that It's not filipino subject. It is Science or in History

The Caspian Sea is the largest enclosed inland body of water onEarth by area, variously classed as theworld's largest lake or a full-fledged sea. It is in an endorheic basin (it has no outflows) located between Europe andAsia. It is bounded to the northeast byKazakhstan, to the northwest by Russia, to the west by Azerbaijan, to the south by Iran, and to the southeast byTurkmenistan.

The Caspian Sea lies to the east of theCaucasus Mountains and to the west of the vast steppe of Central Asia. Its northern part, the Caspian Depression, is one of the lowest points on Earth. The ancient inhabitants of its coast perceived the Caspian Sea as an ocean, probably because of its saltiness and large size.

The word Caspian is derived from the name of the Caspi, an ancient people who lived to the southwest of the sea inTranscaucasia. Strabo wrote that "tothe country of the Albanians belongs also the territory called Caspiane, which was named after the Caspian tribe, as was also the sea; but the tribe has now disappeared". Moreover, the Caspian Gates, which is the name of a region inIran's Tehran province, possibly indicates that they migrated to the south of the sea. The Iranian city of Qazvinshares the root of its name with that of the sea. In fact, the traditional Arabic name for the sea itself is Bahr al-Qazwin (Sea of Qazvin).

In classical antiquity among Greeks and Persians it was called the HyrcanianOcean. In Persian antiquity, as well as in modern Iran, it is known as theMazandaran Sea (Persian: دریای مازندران‎‎); it is also sometimes referred to as دریای خزر, Daryā-e Khazar in Iran. Ancient Arabic sources refer to it as Baḥr Gīlān(بحر گیلان) meaning "the Gilan Sea".

Turkic languages refer to the lake asKhazar Sea. In Turkmen, the name isHazar deňizi, in Azeri, it is Xəzər dənizi, and in modern Turkish, it is Hazar denizi. In all these cases, the second word simply means "sea", and the first word refers to the historical Khazars who had a large empire based to the north of the Caspian Sea between the 7th and 10th centuries. An exception is Kazakh, where it is called Каспий теңізі, Kaspiy teñizi (Caspian Sea).

Old Russian sources call it the Khvalynor Khvalis Sea (Хвалынское море / Хвалисское море) after the name ofKhwarezmia. In modern Russian, it is called Каспи́йское мо́ре, Kaspiyskoye more.