Almost every person who has gone through the American public school system knows the words “vowel” and “consonant.” They can recite the vowels —  “a, e, i, o, u and sometimes y” — and they know that everything else is a consonant. But can they tell you what a vowel is? And what about consonants?

In a recent episode of Jimmy Kimmel, people exercising were asked whether they abstained from gluten, to which all those interviewed responded “yes.” They were then asked whether they knew what gluten actually was. Most just listed things they knew contained gluten (bread, beer, etc.), but none of them could actually explain what it was they were actually avoiding. Our K-12 knowledge of consonants and vowels is a little bit like common knowledge of gluten. We have a vague idea what sorts of things fall into those categories,  but we don’t have a clear idea of what the words “vowel” and “consonant” actually mean. Add to that the fact that our spelling system is quite divorced from the realities of our language’s sounds, and it’s no wonder that the concept is confusing. Luckily for you, your friendly neighborhood linguistics blogger is here to clear all that up for you!

What is a consonant?

Consonants are often ignored in our elementary education. Vowels are defined by the letters which (usually) represent them, but consonants are basically left unspoken of, defined only by their existence as not-vowels. Consonants are essentially this: there is constriction in the vocal tract, resulting in the cutting-off or muting of sound. This can be a total cutting off of sound, like the English sounds k as in “key”, or it can be a more subtle constriction, like the “th” in “the.”

What is a vowel?

Whereas consonants have definite constrictions, vowels use the smallest amount of constriction possible. This leaves lots of space in the mouth for vowels to resonate. Say the sound “s” as in “sign” a couple times in a row; then say the sound “z” as in “zebra.” The only difference between the sounds is voicing; put your finger on your larynx (your Adam’s Apple, if you’re a man) and notice that it vibrates for the sound “z” but not for the sound “s.” That vibration is called “voicing.” All vowels are voiced (say “aaaaah” with your fingers on your larynx), but many consonants are not. This also makes vowels much louder than consonants.

To see this in action, take a look at the picture below. It contains what linguists call a “waveform.” The waveform basically shows us how loud each part of a word is. The word represented below is “papi.” Notice the small amplitude at the very beginning (in the first red circle), and how it grows into a much louder part of the waveform (the “a” in “papi”, represented by the green line), followed by a period of total silence, which is the closure of the second “p” (the second red circle), followed by another vowel, “i” (with a blue line). The “i” is smaller than the “a” because the sound “a” is said with the mouth wide open, whereas “i” is said with a narrower mouth opening (remember my post on sound symbolism?).

Via the Aristotle University of Thessaloniki School of English

The in-betweens

Unfortunately, the difference between vowels and consonants isn’t so cut and dry. There are a number of sounds that are a bit fuzzier. Two sounds in English — w and y — are called “glides” or “semi-vowels”, and they have vowel-like qualities while still being consonants. For example, have you ever noticed in words like “being,” we actually pronounce it like “bee-ying”? Glides connect two vowels to each other and act as consonants when we need them to, in words like “yard” and “war.”

So we have consonants that look like vowels, so what about vowels that look like consonants? The following sounds can be what linguists call “syllabic sonorants”: m, n, l, r. These sounds can function as consonants, in words like “mother” and “nose” and “light” and “rare.” However, these sounds can also be vowels, in “syllabic sonorants.” Consider the word “bird.” Try to break it down into the sounds you would expect it to have: “B” + “ih” + “r” + “d”. It’s not quite what you’d expect, right? Sounds like someone saying a weird version of the word “beard,” rather than the way you know “bird” to be pronounced. That’s because the sounds in bird are actually just “b” + “r” + “d.” The “r” is the vowel. This is also the case for the other three sounds. Think of the m in “prism”, the last syllable in “kitten” and “ladle.” All of these sounds are just vowel versions of r, m, n, and l.

It turns out that consonants and vowels are not actually as distinct of categories as we might like to imagine. Speech sounds form more of a spectrum of sounds, with some sounds between our tidy categories of consonants and vowels.