U-breve

Ŭ or ŭ is a letter in the Esperanto alphabet, based on u. It is also used in the Belarusian language, when written in the 20th-century form of the Belarusian Latin alphabet. The accent mark (diacritic) is known as a breve.

This letter should not be confused with u-caron, which is used to indicate u in the third tone of Chinese language pinyin; Compare Ǔ ǔ (caron) with Ŭ ŭ (breve).

The letter ŭ is called non-syllabic u (romanised: u nieskładovaje) in Belarusian because it resembles the vowel u but forms no syllables. It is an allophone of /v/ that forms the diphthongs aŭ, eŭ, oŭ and is equivalent to [u̯]. Its Cyrillic counterpart is ў. Sometimes (as in National Geographic atlases), the Cyrillic letter ў is Romanized as w.

Ŭ represents a semivowel in the orthography of Esperanto, which is an international auxiliary language publicly presented in 1887. As in Belarusian, Esperanto Ŭ is pronounced as a non-syllabic [u̯], primarily in the diphthongs aŭ and eŭ.

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