of sonorants and continuants. Before Peter Ladefoged coined the term approximant in the 1960s, the terms frictionless continuant and semivowel were used Approximants are speech sounds that involve the articulators approaching each other but not narrowly enough, nor with enough articulatory precision, to create turbulent airflow. Therefore, approximants fall between fricatives, which have a degree of constriction tight enough to produce a turbulent airstream, and vowels, which have no constriction. This class includes vowel-like sounds such as [j] Some approximants resemble vowels in acoustic and articulatory properties and the terms semivowel and glide are often used for these non-syllabic vowel-like segments. The correlation between semivowels and vowels is strong enough that cross-language differences between semivowels correspond with the differences between their related vowels. Semivowels may be distinguished from the rest of approximants via a feature of prolongability; while all other approximants are prolongable, semivowels are momentary, as prolonging them results instead in the formation of their vocalic equivalents ([j, w] → [i, u]). Vowels and their corresponding semivowels alternate in many languages depending on the phonological environment, or for grammatical reasons, as is the case with Indo-European ablaut. Similarly, languages often avoid configurations where a semivowel precedes its corresponding vowel. A number of phoneticians distinguish between semivowels and approximants by their location in a syllable. Although he uses the terms interchangeably, Montreuil (2004, p. 104) remarks that, for example, the final glides of English par and buy differ from French par ('through') and baille ('tub') in that in the French examples, the approximants appear in the syllable coda, whereas in the English ones, they appear in the syllable nucleus. This means that opaque (if not minimal) contrasts can occur in languages like Italian (with the i-like sound of piede 'foot', appearing in the nucleus: [ˈpi̯ɛˑde], and that of piano 'plane', appearing in the syllable onset: [ˈpjaˑno]) and Spanish (with a near minimal pair being abyecto [aβˈjekto] 'abject' and abierto [aˈβi̯erto] 'opened'). In a related sense, the terms semivowel and semiconsonant are often treated as synonyms in English linguistic tradition, though the latter may be regarded as somewhat antiquated. However, in other linguistic traditions, a distinction is made between the two terms. In these traditions, semivowels refer to non-syllabic vowel offglides (such as [i̯, u̯]) often found as partial components of syllable nuclei (such as in diphthongs), while semiconsonants refer to consonant onglides (such as [j, w]) often found in syllable… The…