 Although "semivowel" and "approximant" are sometimes treated as synonymous, most authors use the term "approximant" for a more restricted set; there is no universally agreed upon definition, and the exact details may vary from author to author.For example, do not consider the labiodental approximant to be a semivowel while proposes that it should be considered one.In the International Phonetic Alphabet, the diacritic attached to non-syllabic vowel letters is an inverted breve placed below the symbol representing the vowel