In just about every respect r behaves like the two glides: w and j. So Why exactly is it not classed as a glide? It is particularly its intrusive behaviour that makes me wonder why.

  • 2
    What evidence do you have that it is not a liquid? Why would you say such a thing? What evidence do you have that anyone classifies /w,j/ as liquids?
    – user6726
    Oct 6, 2016 at 4:16
  • Epic blunder on my side. Five am was early indeed, it seems... So the question was meant to be: Why is r not a glide? Oct 6, 2016 at 9:26
  • I never understood the differences between glides and syllabic consonants. R is syllabic in many languages. Oct 6, 2016 at 10:28

2 Answers 2


It depends on the language (note that there are many kinds of "r" and IPA has a wealth of r-like letters to indicate some of those differences). In very many languages, [r] or [ɾ] (etc.) is not treated as a glide, because it acts differently from glides. For example, onset clusters in Chinese can include glides, but not r. There is a common syllabification rule that syllables can end with glide plus consonant, but not liquid or nasal plus consonant, and r acts like a linquid rather than a glide. However English [ɹ] is rather different. In terms of features, r is usually [+consonantal] (which has to do with there being a constriction in the vocal tract smaller than a certain size), but English [ɹ] is very unconstricted and it is [-consonantal]. So it does in fact act like a glide, and is treated as a glide. The moral of the story is that not all rs are the same, and not all treatments of r are the same.

  • What's the argument for treating English [ɹ] as [-consonantal]?
    – TKR
    Oct 6, 2016 at 20:26
  • It's strictly based on the phonetics: the constriction is only a bit narrower at the tongue dorsum than with [w]. Otherwise, it's the patterning fact. Since I'm actually skeptical about using phonetics as the court of appeals for features assignment, I think there is just the patterning fact and that [cons] nonsyllabic means "glide".
    – user6726
    Oct 6, 2016 at 20:49
  • Sorry, what is the patterning fact?
    – TKR
    Oct 6, 2016 at 20:55

Why does it matter? If we start calling it a glide, does that predict it can be intrusive? How?

Historically, in Preliminaries to Speech Analysis, IIRC, an acoustic account was given for classifying r/l as both consonantal and vocalic, as compared to the glides, which have neither property. Something about having zeros in the spectrum and having periodic properties. I don't believe in acoustic features, so I have a hard time caring.

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