It looks similar to the circumflex (ˆ), which has a sharp tip (Â â Ê ê Î î Ô ô Û û), while the inverted breve is rounded: (Ȃ ȃ Ȇ ȇ Ȋ ȋ Ȏ ȏ Ȗ ȗ).
The inverted breve above is used in traditional Slavicist notation of Serbo-Croatian phonology to indicate long falling accent.
In the early 19th century, it began to be used in both Latin and Cyrillic as a diacritic to mark prosody in the systematic study of the Serbo-Croatian linguistic continuum.
The diacritic thus expands upon the four primary symbols [j, w, ɥ, ɰ] the IPA reserves for semivowels, which correspond to the full vowels [i, u, y, ɯ], respectively.
The same diacritic is placed under iota (ι̯) to represent the Proto-Indo-European semivowel *y as it relates to Greek grammar; upsilon with an inverted breve (υ̯) is used alongside digamma (ϝ) to represent the Proto-Indo-European semivowel *w.[1] Inverted breve characters are supported in Unicode and HTML code (decimal numeric character reference).