Language & WorldFact
The world's largest lake is called a "sea".
The Caspian Sea has no outlet to the ocean, which makes it a lake, and at about 371,000 km² the largest on Earth, bigger than Germany. Its water is salty, but only about a third as salty as the ocean. Whether it legally counts as lake or sea was disputed for decades, because that decides how oil fields are split.
Useful: Names on maps are historical, not scientific; "sea" doesn't guarantee an ocean.
Source: en.wikipedia.org