International Phonetic Alphabet - Wikipedia
https://en.wikipedia.org/wiki/International_Phonetic_AlphabetA number of IPA letters and diacritics have been retired or replaced over the years. This number includes duplicate symbols, symbols that were replaced due to user preference, and unitary symbols that were rendered with diacritics or digraphs to reduce the inventory of the IPA. The rejected symbols are now considered obsolete, though some are still seen in the literature. The IPA once had several pairs of duplicate symbols from alternative proposals, but eventually s…