Mainland China in the context of "Hong Kong"

The East China Sea is a marginal sea of the Western Pacific Ocean, located directly offshore from East China. China names the body of water along its eastern coast as "East Sea" (Dōng Hǎi, simplified Chinese: 东海; traditional Chinese: 東海) due to direction, the name of "East China Sea" is otherwise designated as a formal name by International Hydrographic Organization (IHO) and used internationally.

It covers an area of roughly 1,249,000 square kilometers (482,000 sq mi). The sea's northern extension between Korean Peninsula and mainland China is the Yellow Sea, separated by an imaginary line between the southwestern tip of South Korea's Jeju Island and the eastern tip of Qidong at the Yangtze River estuary.

Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main island of Taiwan, also known as Formosa, lies between the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northeast, and the Philippines to the south. It has an area of 35,808 square kilometres (13,826 square miles), with mountain ranges dominating the eastern two-thirds and plains in the western third, where its highly urbanized population is concentrated. The combined territories under ROC control consist of 168 islands in total covering 36,193 square kilometres (13,974 square miles). The largest metropolitan area is formed by Taipei (the capital), New Taipei City, and Keelung. With around 23.9 million inhabitants, Taiwan is among the most densely populated countries.

Taiwan has been settled for at least 25,000 years. Ancestors of Taiwanese indigenous peoples settled the island around 6,000 years ago. In the 17th century, large-scale Han Chinese immigration began under Dutch colonial rule and continued under the Kingdom of Tungning, the first predominantly Han Chinese state in Taiwanese history. The island was annexed in 1683 by the Qing dynasty and ceded to the Empire of Japan in 1895. The Republic of China, which had overthrown the Qing in 1912 under the leadership of Sun Yat-sen, assumed control following the surrender of Japan in World War II. But with the loss of mainland China to the Communists in the Chinese Civil War, the government moved to Taiwan in 1949 under the Kuomintang (KMT).

Chinese characters are logographs used to write the Chinese languages and others from regions historically influenced by Chinese culture. Of the four independently invented writing systems accepted by scholars, they represent the only one that has remained in continuous use. Over a documented history spanning more than three millennia, the function, style, and means of writing characters have changed greatly. Unlike letters in alphabets that reflect the sounds of speech, Chinese characters generally represent morphemes, the units of meaning in a language. Writing all of the frequently used vocabulary in a language requires roughly 2000–3000 characters; as of 2025, more than 100000 have been identified and included in The Unicode Standard. Characters are created according to several principles, where aspects of shape and pronunciation may be used to indicate the character's meaning.

The first attested characters are oracle bone inscriptions made during the 13th century BCE in what is now Anyang, Henan, as part of divinations conducted by the Shang dynasty royal house. Character forms were originally ideographic or pictographic in style, but evolved as writing spread across China. Numerous attempts have been made to reform the script, including the promotion of small seal script by the Qin dynasty (221–206 BCE). Clerical script, which had matured by the early Han dynasty (202 BCE – 220 CE), abstracted the forms of characters—obscuring their pictographic origins in favour of making them easier to write. Following the Han, regular script emerged as the result of cursive influence on clerical script, and has been the primary style used for characters since. Informed by a long tradition of lexicography, states using Chinese characters have standardized their forms—broadly, simplified characters are used to write Chinese in mainland China, Singapore, and Malaysia, while traditional characters are used in Taiwan, Hong Kong, and Macau.

Macau or Macao is a special administrative region of the People's Republic of China (PRC). With a population of about 710,000 people and a land area of 32.9 km (12.7 sq mi), it is the most densely populated region in the world.

Formerly a Portuguese colony, the territory of Portuguese Macau was first leased to Portugal by the Ming dynasty as a trading post in 1557. Portugal paid an annual rent and administered the territory under Chinese sovereignty until 1887, when Portugal gained perpetual colonial rights with the signing of the Sino-Portuguese Treaty of Peking. The colony remained under Portuguese rule until the 1999 handover to China. Macau is a special administrative region of China, which maintains separate governing and economic systems from those of mainland China under the principle of "one country, two systems". The unique blend of Portuguese and Chinese architecture in the city's historic centre has resulted in its designation as a UNESCO World Heritage Site in 2005.

Simplified Chinese characters are one of two standardized character sets widely used to write the Chinese language, with the other being traditional characters. Their mass standardization during the 20th century was part of an initiative by the People's Republic of China (PRC) to promote literacy, and their use in ordinary circumstances on the mainland has been encouraged by the Chinese government since the 1950s. They are the standard forms used in mainland China, Malaysia, and Singapore, while traditional characters are officially used in Hong Kong, Macau, and Taiwan.

Simplification of a component—either a character or a sub-component called a radical—usually involves either a reduction in its total number of strokes, or an apparent streamlining of which strokes are chosen in what places—for example, the ⼓ 'WRAP' radical used in the traditional character 沒 is simplified to ⼏ 'TABLE' to form the simplified character 没. By systematically simplifying radicals, large swaths of the character set are altered. Some simplifications were based on popular cursive forms that embody graphic or phonetic simplifications of the traditional forms. In addition, variant characters with identical pronunciation and meaning were reduced to a single standardized character, usually the simplest among all variants in form. Finally, many characters were left untouched by simplification and are thus identical between the traditional and simplified Chinese orthographies.

Traditional Chinese characters are a standard set of Chinese character forms used to write Chinese languages. In Taiwan, the set of traditional characters is regulated by the Ministry of Education and standardized in the Standard Form of National Characters. These forms were predominant in written Chinese until the middle of the 20th century, when various countries that use Chinese characters began standardizing simplified sets of characters, often with characters that existed before as well-known variants of the predominant forms.

Simplified characters as codified by the People's Republic of China are predominantly used in mainland China, Malaysia, and Singapore. "Traditional" as such is a retronym applied to non-simplified character sets in the wake of widespread use of simplified characters. Traditional characters are commonly used in Taiwan, Hong Kong, and Macau, as well as in most overseas Chinese communities outside of Southeast Asia. As for non-Chinese languages written using Chinese characters, Japanese kanji include many simplified characters known as shinjitai standardized after World War II, sometimes distinct from their simplified Chinese counterparts. Korean hanja, still used to a certain extent in South Korea, remain virtually identical to traditional characters, with variations between the two forms largely stylistic.

The Yellow Sea (simplified Chinese: 黄海; traditional Chinese: 黃海; pinyin: Huáng Hǎi; Korean: 황해; Hanja: 黃海; RR: Hwanghae), also known as the North Sea, is a marginal sea of the Western Pacific Ocean located between mainland China and the Korean Peninsula, and can be considered the northwestern part of the East China Sea.