There are a variety of obsolete and nonstandard symbols that have been used in and alongside the International Phonetic Alphabet (IPA). These fall into a few basic categories, including:Those used historically in the IPA Some represent standard phonetic values that have been modified or replaced completely, such as ⟨ɩ ɷ⟩ for modern Others represent varied manners and places of articulation, phonation states, or sounds paired with secondary articulation, that have been dropped altogether with the idea that they should instead be indicated with diacritics, such as ⟨ƥ ƭ ƙ⟩ for modern Those specific to local linguistic traditions that otherwise use standard IPA Some represent sounds in a more simplified form, such as the Americanist ⟨ƛ λ⟩ for standard Others represent phonemes and phones that may be generally difficult to describe with the usage of standard letters and diacritics, such as the Sinologist ⟨ɿ ʮ⟩ for so-called "apical vowels" Those which fill in "gaps" of the IPA chart Some are "implicit" or "expected" symbols created or used by iconographic analogy to symbols for related sounds, such as ⟨ᴘ 𝼈 ⟩ for Others are simply created or used for common sounds that lack independent symbols, such as ⟨ᴀ ᴇ ꭥ⟩ for Those applying to any of the above categories that have been proposed for usage in or adjacent to the IPA Some have been formally proposed to and rejected by the International Phonetic Association, many of which have been largely or entirely unused outside of their respective proposals Others have been informally proposed and occasionally used but have lacked widespread consensus in their usage, often being idiosyncratic or seeing a number of competing proposals to represent a sound