Difference Between Sea and Ocean


Main Difference

Many people use the terms sea and ocean thinking they are the same thing, but there are major differences between them. To understand the way in which they differ, we need to look at their definition. Both the terms are considered synonyms of each other which are not entirely accurate. Ocean is a large part of the water that spreads all over the world. Although oceans are divided into different parts and names, they are mainly connected and form one vast world ocean. Sea, on the other hand, is water that covers most of the surface and is adjoined by land. There are many different seas in the world which have various names depending on their location. The main difference between them is that oceans are larger while seas are smaller in sizes. Another major difference between them is that oceans are deeper as compared to seas which may or may not be deep. Most of the oceans fall in the region of the abyssopelagic zone in which any kind of water that is present is no way near the shores and deeper than usual. Therefore, seas are not as unfathomable as compared to oceans. Because the sea is always near land the wildlife, it has consisted of a variety of species while oceans have few species which mostly are bacteria or other plants. Oceans can influence the world’s weather when they transfer currents which result in the hot or cold air while seas are not able to do that, and themselves depend on oceans. There are five main oceans one planet earth while the number of seas is numerous. A sea can be part of an ocean while ocean cannot be a part of the sea. The biggest sea is smaller than the smallest ocean which gives an idea of how big the difference between the two can be.

Comparison Chart

A large body of water constituting a principal part of the hydrosphere.A division of an ocean or a large body of salt water partially enclosed by land.
There are 5 oceans in the worldThere are numerous seas in the world
IndependentUsed as a synonym for Ocean
Oceans are deeperSea is not as deep as an ocean
Oceans can affect the climateSeas have no bearing on the climate

Definition of Ocean

Ocean is a big reservoir of water that is spread all over the world. There are five main oceans which have been named because of their location, they are Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean, and the Southern Ocean. They make up almost 70% of the total area of the planet earth and have more than 95% of the total water that is present. Although they have been divided in different names, it is a continuous stream of water which is not separated by land. Therefore, oceans can be defined as water that is not surrounded by land. Due to this factor, most of the oceans are very deep and do not have any particular wildlife among them. They play a prominent role in shaping the world’s atmosphere and their currents which bring different types of winds across the globe help in defining the weather conditions. The major Ocean is the Pacific Ocean, which is twice the size of the second largest one. In a bigger perceptive it can be said that it is the land that is a part of oceans instead of saying that oceans are a part of this planet.


Definition of Sea

Sea is smaller than oceans but larger than rivers, the thing that differentiates them from others is that they have shore with them which connect them with the peace of land. Many different seas are depending on the location, and the biggest sea which is the Mediterranean is smaller than the Arctic Ocean which is the littlest among the five. Since sea has land connecting, they have a variety of wildlife present which can include fishes, animals, birds and even plants and bacteria. They are not as deep as compared to oceans because they have land connecting. The best way to define sea is that they are the part connecting the ocean with the land. Sea does not have the ability to influence anything on earth and actually are dependent on the oceans for any changes. Most of the seas fall I the epipelagic and mesopelagic zones which are near the surface of land and are part of the water which is not considered bottomless.

Differences in a Nutshell

  1. There are 5 main oceans in the world while there are numerous seas which are present on the globe.
  2. Oceans are a continuous stream of water that has just been divided by regions while seas are separate.
  3. Oceans do not have any type of land near them while seas have their own shores.
  4. Oceans are deeper while seas are not as thick as compared to oceans.
  5. Oceans are not part of any sea, but all the seas are part of the oceans.
  6. Oceans do not have any substantial wildlife present in them since they are away from the land. Seas, on the other hand, have a variety of animal and plant life because of favorable conditions.
  7. Oceans have the ability to change the climate of the globe, but seas do not have that influence on the weather.
  8. Most oceans fall in the abyssopelagic and hadopelagic zones which are deep while seas fall in the epipelagic and mesopelagic zones which are near the surface of the land.


All in all, it can be said that the two terms are closely related to each other but are different in the way they are used and how people perceive it. Hopefully this article would have helped in understanding those differences in a proper manner.

Aimie Carlson

Aimie Carlson is an English language enthusiast who loves writing and has a master degree in English literature. Follow her on Twitter at @AimieCarlson