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Ŝ or ŝ (S circumflex) is a consonant in Esperanto orthography, representing the sound [ʃ].
Esperanto orthography uses a diacritic for all four of its postalveolar consonants, as do most Latin-based Slavic alphabets (Polish is the most notable exception). Letters and digraphs that are similar to ŝ (also based on s) and represent the same sound include Czech, Slovak, Slovene, Serbian Latin, and Croatian š, and English sh", and Portuguese "x","ch". The Cyrillic letter ш represents the same sound.
Ŝ is used in ISO 9:1995 (standard of transliteration into Latin characters of Cyrillic characters) for letter Щ.
Ŝ is the twenty-third letter of the Esperanto alphabet. Although it is written as sx and sh respectively in the x-system and h-system workarounds, it is normally written as S with a circumflex: ŝ.