The West Philippine Sea and the South China Sea are all over the headlines again following China's increasing activities in the said waters.

The two terms are not necessarily the same and interchangeable, though. And not everybody knows about it.

So here's the difference.
West Philippine Sea (WPS) - Located west of the Philippines, the West Philippine Sea is only part of the bigger South China Sea.

The term is used to refer to the waters included in the Philippines' exclusive economic zone (EEZ), which covers up to 200 nautical miles (370 kilometers) from the Philippine shores.

WPS was first used by the Philippine government in 2011 for purposes of the national mapping system as well as to symbolize its disagreement with China's sovereignty claim over the whole South China Sea.

South China Sea (SCS) - The South China Sea encompasses a surface area of 3.5 million square-kilometer (1.4 square miles). Within it is the West Philippine Sea.

SCS is located south of China and Taiwan; west of the Philippines, Indonesia and Brunei; north of Malaysia; and east of Vietnam.

The countries surrounding SCS are also the countries that have claims over it.

But it is only China that has a competing claim against the Philippines. So we will focus on that.

China's claim - Unlike other countries, China is the only one claiming the entirety of the South China Sea. That means it includes the West Philippine Sea. Its claim is based on a historic nine-dash line, which came from the initial U-shaped eleven-dash line originally published by the government of the Republic of China (Taiwan) in December 1947.

Philippines' claim - Meanwhile, the Philippines is claiming only a part of the South China Sea—that is the West Philippine Sea. In its claim, the Philippines cites historical documents, the United Nations Convention on the Law of the Sea (UNCLOS) and the 2016 Arbitral Ruling.

Among records that the Philippines bases on is a historical map that was called the Velarde map. It was first published in Manila in 1734 by Jesuit cartographer Pedro Murillo Velarde, engraver Nicolás de la Cruz Bagay and artist Francisco Suárez.

Interestingly, the map featured not only the West Philippine Sea but also the Scarborough Shoal, which is located 220 kilometers away from Luzon.

Meanwhile, the 1982 United Nations Convention on the Law of the Sea puts in better position the Philippine claim over the West Philippine Sea.

It's because under the treaty, a country's EEZ generally extends to 200 nautical miles from its shore, within which the coastal state has the right to explore and exploit, and the responsibility to conserve and manage, both living and non-living resources.

The treaty was ratified by 168 state parties, including China and the Philippines.

In 2016, the Philippine claim on the West Philippine Sea was validated by a ruling after the country brought an arbitration case against China under Annex VII of the UNCLOS.

Basically, the ruling turned in favor of the Philippines, concluding that, in the matter of China's claims of historical rights and its nine-dash line, China had no legal basis to claim historical rights to resources within the sea areas falling within the nine-dash line.

The Tribunal also found that China and other states had historically made use of the islands in the South China Sea, but it found no evidence that China had historically exercised exclusive control over the waters and their resources.

Stating in February 2013 that it would not participate in the arbitration, China has been rejecting the ruling until now.

Spratly Islands - The Spratly Islands is an archipelago composed of over a dozen islands as well as several islets, cays and reefs.

Only the northeastern section of this group of islands is being claimed by the Philippines, which calls it Kalayaan Island Group (KIG). China, on the other hand, claims the entire archipelago.

The Tribunal declared that Spratly islands are within the EEZ of the Philippines.

Under the provision of UNCLOS, "rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf."

Since none of the features claimed by China was capable of generating an exclusive economic zone, the Tribunal found that it could—without delimiting a boundary—declare that certain sea areas are within the exclusive economic zone of the Philippines, because those areas are not overlapped by any possible entitlement of China.