Look at all the ascenders in this word: three tall l’s, a b, two dots on i’s – like a tongue reaching up in the mouth, perhaps. And just one descender, on the g. It has those three liquids on tongue tip; in between them you have the tongue touching at the back once, and the lips meeting once. It has a nice balance: six consonants and six vowel letters – you might say the uo is really a diphthong, though you probably won’t say ai as a diphthong. And it’s three of each for each half of the word. What’s more, the two morphemes that make this word meet at exactly the halfway point. It’s like a sound that’s, say, half tongue and half lip.
Which is what linguolabial refers to. The labial refers to the lips, as you likely know. The linguo refers to the tongue – it’s a root that gets around: linguistics is the study of languages, and even language traces back to that tongue root. It is not your vocal cords or even your lips that make the speech, nor is it in this presentation your brain; it is your tongue, that most lithe and lively little muscle, that is the heart and soul of language.
But how often does tongue meet lips? In speech in English and many other languages, while we require the lips to set the boundary of the resonating space in the mouth and the tongue to configure the resonances within that space, we keep them working indpendently, like distant colleagues in separate offices. But a few languages (some in the Pacific islands and some in Africa, for instance) bring them together, in close contact, to make consonants.
Say “mmmm.” Your lips are closed and your tongue is relaxed. Now say “nnnn.” Your lips are open and your tongue is touching the roof of your mouth. Now put your tongue against your upper lip, all the way across, and say whatever version of “mmmm” or “nnnn” it will allow. And what version is that? What is that sound? Even the International Phonetic Alphabet has two ways of writing it. The symbol for “linguolabial” is a little double-humped thing, like a pair of wings or a top lip, that is put below the consonant symbol. But which consonant? Is what you’ve just made a linguolabial [m] or [n]? Well, yes. Both and neither. So either may be used, with the linguolabial diacritic (the symbol I just mentioned). The same goes for voiced and voiceless stops and fricatives and liquids.
I’m actually not sure if any language uses a linguolabial liquid, which would be [l] with the tongue against the upper lip rather than the roof of the mouth. But you can make one: just lick your tongue across your upper lip and, when it’s in the middle, stop and just make a sound with your voice.
Of course, even speakers of languages that don’t have linguolabials do put their tongues to their lips – just not for making sounds that go into words. The colleagues from different offices (tongue and lip) may not work directly together for their jobs, but they get together recreationally.
But speaking of getting together recreationally, here’s a thing to try if you have the opportunity. The sounds we make are affected by the shape of the articulatory space as determined by the tongue position. Wouldn’t you like to know what difference it would make if the tongue were coming from the opposite angle? Find someone with whom you are on kissing-on-the-lips terms, or are about to be. You know what a linguolabial sounds like when you make it with your tongue and lip. See what sound you get if you use your tongue on the other person’s lip, or vice versa. You won’t be able to do a stop or a nasal, because you can’t block the other person’s airflow (with bilabial-bilabial you can, but that’s not in the IPA because it requires two-person articulation and what language would require that?). But you can try a liquid, that linguolabial [l]. Try it a few times. What do you hear?