Hmmm geographic differences.. I can sort of explain this^^ The oceans are the (five) major bodies of water covering our planet: The Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic ocean. A sea is a large body of salt water connected to an ocean. Example: The Mediterranean Sea. Its a large body of water surrounded by land, with an outlet to an ocean. But "sea" can also be a synonym for ocean... Sometimes you might hear someone say that they are going to "swim in the sea," but they're technically swimming in an ocean. And it's perfectly acceptable to use it this way. Plural or singluar It depends on your context and words of choice. Oceans are countable so you can use "all" and "every"- they both mean the same thing! But... When using "all", the noun (ocean/sea) is plural. When using "every", the noun is singular. Examples: I want to swim in all five oceans. (all = plural noun) I want to swim in every ocean. (every = singular noun) And otherwise, when talking about more than one, add the -s The oceans are too big to swim across. These are the coldest seas on Earth. And I would say, "I found a seastar in the ocean!"

bigger smaller :P

technically no difference! symbolistically, the one you may want to add! can be used both in singular and plural. "the ocean is the ultimate solution",,,(frank zappa's composition title) "your eyes are like a deep blue sea" (some other song, but i cant remember which one) "I have travelled by all the seven seas and the five oceans of this world" (no song, many buccaneers say this in the tales of adventures,,,like Simbad or Stevenson, Melville, etc)

Like atlantic ocean an baltic sea. Atlantic, pacific, arctic, indian. Are all oceans. What is left: seas, lakes rivers and puddles (or poodles?) ^_~