Sources

"Ocean Facts." National Ocean Service. 17 June, 2013. Web. 1 Dec 2013. <http://oceanservice.noaa.gov/facts/oceanorsea.html>.

Griffin, Brian. "What's the difference between a sea and an ocean?" Whyzz.com. n.d. Web. 1 Dec 2013. <
http://www.whyzz.com/whats-the-difference-between-a-sea-and-an-ocean>.
"Sea." National Geographic. n.d. Web. 1 Dec 2013. <
http://education.nationalgeographic.com/education/encyclopedia/sea/?ar_a=1>.

"Caspian Sea & Neighbours." International Studies for Caspian Studies. n.d. Web. 1 Dec 2013. <http://www.caspianstudies.com/Links/Country/Caspian.html>.

 

What is the difference between an Ocean and a Sea?

People often use the terms "ocean" and "sea" interchangeably. However, there is a difference between the two terms. Oceans are very large bodies of water that covers three-quarters of the earth’s surface.  
The five oceans in descending order of area are the Pacific, Atlantic,
Indian, Southern, and Arctic Oceans. These oceans comprise the “world ocean.” 

A Sea, on the other hand, is much smaller and is usually located where
the land and ocean meet. A sea can be partially or completely enclosed by land. 

The Red Sea and Yellow Sea are examples of marginal seas. The Red Sea is connected to the Indian Ocean by a narrow strait called Bab-el-Mandeb. The Yellow Sea is the name given to the northern part of the East China Sea, which is a marginal sea of the Pacific Ocean. It is located between mainland China and the Korean Peninsula. 

The Caspian Sea is an example of a landlocked sea located between Asia and Europe.