A breve is a diacritical mark like a little round cup, in Romanian possible above the a (the Schwa vowel) and in Esperanto possible above the u:

ŭ

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A breve is also a note in music, lasting twice as long as a semibreve (or whole note). Because it lasts longer than a bar[?] in most modern time signatures, it is now rarely encountered, but in Mediaeval music it was the shortest note length, and could be either a half or a third as long as the longa[?].

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Breve is also a Spanish language word meaning Shortly. For example, if someone says Voy a hacerlo en breve, it means Im gonna do it shortly.