Zhuyin Fuhao, often shortened as zhuyin and commonly called bopomofo, is a type of sound-based writing for the Chinese language. In Chinese, "bo", "po", "mo" and "fo" are the first four of the conventional ordering of available syllables.
Zhuyin was introduced in China by the Republicans in the 1910s and used alongside the Wade-Giles system, which used a Latin alphabet. The Wade system was replaced by Pinyin in 1958 by the Communist Government.
Zhuyin is widely used in Taiwan, where it is known as "bopomofo" and is the primary method for teaching reading and writing in elementary school. In Hong Kong and Macau, "jyutping" is used for Cantonese. Zhuyin is also used to a certain extent in some Mandarin-speaking communities outside China, such as Singapore and Malaysia.
The Zhuyin characters have some similarities to the Wade-Giles system, but they are not identical. Zhuyin was developed in mainland China and Taiwan has its own version of Zhuyin, which is slightly different.
The basic unit of Zhuyin is the "syllable", which is represented by a single character. Most syllables have three parts: an initial (声母, shengmu), a final (韵母, yunmu), and a tone (声调, shengdiao).
You can also convert between Zhuyin and hanyu pinyin using this app. This converter accepts traditional Chinese and simplified Chinese.