There are many uses for Chinese Romanization. Most broadly, it is used to provide a useful way for foreigners who are not skilled at recognizing Chinese script to read and recognize Chinese. It can also be helpful for clarifying pronunciation among Chinese speakers who speak mutually unintelligible Chinese dialects. Romanization facilitates entering characters on standard keyboards such as QWERTY. Chinese dictionaries have complex and competing sorting rules for characters, and romanization systems simplify the problem by listing characters in their Latin form alphabetically.
The Indian Sanskrit grammarians who went to China two thousand years ago to work on the translation of Buddhist scriptures into Chinese and the transcription of Buddhist terms into Chinese, discovered the "initial sound", "final sound", and "suprasegmental tone" structure of spoken Chinese syllables. This understanding is reflected in the precise Fanqie system, and it is the core principle of all modern systems. While the Fanqie system was ideal for indicating the conventional pronunciation of single, isolated characters in written Classical Chinese literature, it was unworkable for the pronunciation of essentially polysyllabic, colloquial spoken Chinese dialects, such as Mandarin.
Aside from syllable structure, it is also necessary to indicate tones in Chinese romanization. Tones distinguish the definition of all morphemes in Chinese, and the definition of a word is often ambiguous in the absence of tones. Certain systems such as Wade-Giles indicate tone with a number following the syllable: ma1, ma2, ma3, ma4. Others, like Pinyin, indicate the tone with diacritics: mā, má, mǎ, mà. Still, the system of Gwoyeu Romatzyh (National Romanization) bypasses the issue of introducing non-letter symbols by changing the letters within the syllable, as in mha, ma, maa, mah, each of which contains the same vowel, but a different tone.
The Wade, Wade-Giles, and Postal systems still appear in the European literature, but generally only within a passage cited from an earlier work. Most European language texts use the Chinese Hanyu Pinyin system (usually without tone marks) since 1979 as it was adopted by the People's Republic of China.
The first consistent system for transcribing Chinese words in Latin alphabet is thought to have been designed in 1583-88 by Matteo Ricci and Michele Ruggieri for their Portuguese-Chinese dictionary — the first ever European-Chinese dictionary. Unfortunately, the manuscript was misplaced in the Jesuit Archives in Rome, and not re-discovered until 1934. The dictionary was finally published in 2001. During the winter of 1598, Ricci, with the help of his Jesuit colleague Lazzaro Cattaneo (1560–1640), compiled a Chinese-Portuguese dictionary as well, in which tones of the romanized Chinese syllables were indicated with diacritical marks. This work has also been lost but not rediscovered.