According to Longman Dictionary

"the sea" and "the ocean" are synonyms and mean "the large area of salty water that covers much of the Earth’s surface"

The dictionary also says British people often say "the sea" and American people often say "the ocean".

I live by the sea (British)
I live by the ocean (American)

I did some research and it says "sea" seems to be smaller and "ocean" seems to be bigger.

Technically speaking, the term “sea” is used to describe smaller bodies of water, while the term “oceans” is used to describe larger bodies of water. (source)

My question is:

How do we know which body of salt water is big and which one is small? Can we measure that?

This is my guess, it seems that "a sea" is surrounded by some land and "an ocean" is not.

I asked some people on Quora and they also said the two terms are different. And they also said the reason American people often say "I live by the ocean" because many parts of America are next to the ocean and the reason British people often say "I live by the sea" because many parts of Britain are next to the sea

To sum up, the dictionary says "the sea" and "the ocean" are the same.

Some sources say "the ocean" is bigger than "the sea" but I don't know how to know which is big and which is small?

It seems that large-sized countries like America and India have oceans like the Indian Ocean and Pacific Ocean and small-sized countries like Britain have seas such as the North Sea and the Irish Sea.

Do "the ocean" and "the sea" the same in American and British English?

  • 2
    Interesting question. Coming from Australia, my first reaction was that it's much of a muchness, although there are situations where one is favored over the other. I'd say we favor "ocean" when mainly talking about big bodies of water and "sea" when talking about land and water. But think of all the phrases and it's not fixed: "overseas", "seaside town", "ocean currents", "holiday by the sea (or coast)", "ocean beach" (as opposed to beach along a bay). I can't really pin down an obvious rule, although saying "sea" when you only have a little bit around you makes sense (as in England).
    – ralph.m
    Commented Jun 8, 2023 at 11:24
  • 3
    The UK is surrounded by four "seas": The North Sea, the Irish Sea, The English Channel and the Atlantic Ocean. It's easy to understand why the British are more likely to say they live near the sea than the ocean. There's also the expression, overseas which just means abroad.
    – Mari-Lou A
    Commented Jun 8, 2023 at 12:25
  • Also from Aus, I would say "by the ocean" only to mean on the coast of an ocean, but "by the sea" to mean on the coast more generally.
    – Peter
    Commented Jun 8, 2023 at 12:40
  • @Tom I have noticed a difference between US and UK usage, so you are not imagining it. Usually in the UK "ocean" refers to a vast body of water, such as the Atlantic Ocean. But "sea" is the preferred term for water around the coast that is close to land. It doesn't really matter which word you use though, as both would be understood here, and I suspect using "sea" would be understood just fine in the US.
    – Billy Kerr
    Commented Jun 8, 2023 at 14:44
  • @Mari-LouA - there are actually a couple missing from that map: the Celtic Sea into which Cornwall extends, and the Sea of the Hebrides which between the southern Outer and Inner Hebridean islands.
    – Billy Kerr
    Commented Jun 8, 2023 at 15:17

2 Answers 2


The short answer for English learners is that English speakers sometimes refer to all bodies of salt water as "the sea", even though not all of them are actual seas. The word "ocean" refers only to the Atlantic Ocean, Pacific Ocean, Arctic Ocean, Indian Ocean and Southern Ocean.

Americans use "sea" less often because there are so few named seas in the Americas, and none with the significance of, say, the Baltic Sea or the Mediterranean Sea. Almost all salt water in the Americas is ocean, so Americans just say "ocean".

England, on the other hand, is surrounded by the North Sea, the Irish Sea, and the English Channel. Only Scotland has some Atlantic shore to the northwest. So British people mostly just say "the sea".

Of course, "ocean" and "sea" are also technical terms used in various sciences and are clearly defined in those domains, but that level of detail is beyond the scope of ELL.

  • This is not accurate. No one confuses sea and ocean. And names of oceans and seas are a special case. Americans use sea too. "All the fish in the sea".
    – Lambie
    Commented Jun 8, 2023 at 18:01
  • Note also that in America, large bodies of water are almost always called lakes, even if, like the great salt lake, they would qualify to be 'seas' by most definitions. Commented Jun 8, 2023 at 20:27
  • @RyanJensen The Great Salt Lake is called lake also in Italian; we call it Gran Lago Salato, not Gran Mare Salato. I do not think that is a prerogative American English has.
    – apaderno
    Commented Jun 8, 2023 at 21:16
  • I have not even the slightest emotional investment in this point, so if you disagree with it that doesn't bother me. Whether translation of a name exposes the linguistic culture of the translators the same way assigning of a name exposes the linguistic culture of the namers is for you to judge. Also, when discussing the fine distinctions between nearly-synonymous terms, usage in other languages is rarely a major consideration... Commented Jun 8, 2023 at 21:28
  • @RyanJensen - what about the Salton Sea? Commented Jun 10, 2023 at 21:01

The dictionary definition you are looking at is incomplete

The Sea and the ocean are the same thing - a large body of water not surrounded by land (c.f. lake).

Geographically, there is only one ocean that surrounds all the land on Earth. However, this global ocean is divided up and given proper names, generally five: the Atlantic Ocean, the Pacific Ocean, the Indian Ocean, the Southern Ocean, and the Artic Ocean.

The sea can also refer to this global ocean, but when used as a proper noun, there are a lot more Seas than Oceans. Many of these are part of a named Ocean; for example, the North Sea is the part of the Atlantic between Britain and Northern Europe. These oceanic seas are generally distinctive in some way - mostly surrounded by land, having distinct currents, or being the area affected by major river discharges. Sometimes they're not called seas, particularly when they are mostly surround by land: Gulf, Bay, and Channel are sometimes used instead and these can also be used of smaller bodies of water that would not be considered seas. There can also be seas inside other seas like the Adriatic inside the Metteteranian.

Other seas are not part of named oceans: for example, the Black Sea or the Caspian Sea - the latter is technically a lake as it is not connected to the global ocean at all.

Because of this usage a sea has the connotation of being smaller than an ocean. When used metaphorically "A life on the ocean wave" or "The cruel sea" the words are interchangeable.

However, when used of the specific, i.e. as a shorthand for a specific named bit of water, the sea and the ocean might refer to same thing: that bit of water over there. Which leads us to why there might be a different usage in Britain and the USA.

The names for the bodies of water around Great Britain are (clockwise) the North Sea, the English Channel, the Irish Sea, and the Atlantic Ocean. However, the first three are also part of the Atlantic Ocean. They are also the three that touch the England part of Great Britain - which is where English comes from. So, it's natural for someone from the UK to refer to the water as "the sea"

The bodies of water around the United States are (clockwise) the Atlantic Ocean, the Gulf of Mexico (considered part of the Atlantic), and the Pacific Ocean. So its natural for a North American English speaker to refer to the water as "the ocean" (or "the Gulf" - always capitalised - if they are from a state that borders it).

English often has words like these that are synonyms - except when they aren't. Because English is a mongrel language that swallows up words that other languages leave lying around.

Sea is a Middle English word which means it came from its Germanic roots and has cognates in Dutch (zee) and German (See). Ocean came in from middle French from Latin which got it from Greek which probably got it from a pre-Greek language, it has a modern French cognate (océan).

So, you have Saxons peasants saying "se" and Norman overlords saying "occean" to mean the same thing - the salty water around England. Over time, as people made maps, the big bodies of water got the more prestigious Ocean and the lesser bodies got the peasant's Sea.

  • 1
    The 'North Sea' was also known as the 'German Ocean' until certain events in the early 20th century. It is usual to capitalise 'Ocean' and 'Sea' only when they are part of a proper name such as 'the Pacific Ocean' or 'the Irish Sea'. Commented Jun 8, 2023 at 13:24
  • …but…but… what about sailing the seven seas ;) Commented Jun 8, 2023 at 15:21
  • Yes, the dictionary's entry may be incomplete but this is because it's not an encyclopedia. It gives the definition of a word, its pronunciation, sometimes its history, a few examples of usage, then it will tell us if the word is old fashioned, obsolete, vulgar or formal. Dictionaries do plenty, imagine an entry as large as your answer, and still it would not be sufficient.
    – Mari-Lou A
    Commented Jun 8, 2023 at 15:23
  • Seas can be entirely surrounded by water, as in the case of the Caspian Sea you mentioned, and as specifically stated in the definition you linked for sea: "smaller than an ocean, that is partly or completely surrounded by land" Commented Jun 8, 2023 at 20:29
  • 1
    @MichaelHarvey I assume he meant to say “land” if he meant the Caspian or was thinking of a sea like the Sargasso if he meant water.
    – Dale M
    Commented Jun 10, 2023 at 22:45

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