Approximants

Approximants are a class of consonant sounds produced with a relatively open vocal tract, so that the airstream flows with little or no turbulence. They are sonorants, usually voiced, and behave like vowels in some respects, but function as consonants within syllable structure. The category includes two main groups: central approximants such as [j], [w], and [ɹ], and lateral approximants such as [l].

Articulatoryly, an approximant involves a constriction that is narrower than a vowel but not enough to create a fricative or stop. The articulators approach but do not fully obstruct the airway. The glides [j] (palatal) and [w] (labio-velar) are often described as semivowels; liquids [l] and [ɹ] are central approximants, with [l] being lateral. Most approximants are voiced; voiceless realizations are uncommon and typically arise as allophones in particular phonological contexts.

Approximants are found in languages worldwide and typically appear onsets in the syllable structure CV or CVC. They can function as nucleus in some languages, especially when reduced to syllabic forms, and they often interact with vowels in vowel-consonant sequences. English examples include the palatal approximant [j] in yes, the labio-velar approximant [w] in wet, and the alveolar [l] in lip as well as the rhotic [ɹ] in red. They contrast with related fricatives or stops in languages that maintain such contrasts.

IPA notation for approximants covers several articulations: the palatal [j], the labial-velar [w], the alveolar central approximant [ɹ], the lateral [l], and less common variants such as the velar [ɰ], the labiodental [ʋ], and other regional allophones. In typology, approximants contribute to syllable formation, phonotactics, and stress patterns, and are contrasted with vowels, fricatives, and stops as a distinct class of consonants.