A vowel is the foundation of a spoken syllable and is a speech sound that is made with your lips somewhat open.
Definition
English has 21 consonants and five vowels, correct? Okay, no. Sounds, not letters, are vowels and consonants. There are around twenty vowels and twenty-four consonants, depending on your accent and how thinly you slice them.
An open mouthed sound is referred to as a consonant.
How consonants are produced
Saying consonant sounds involves constricting airflow in different locations in your mouth by:
briefly stopping then releasing the air (“p”, “b”, “t”, “d”, “k”, “g”),
diverting the airflow and associated resonance to your nose (“m”, “n”, “ng”),
squeezing the air through a narrow space (“th” as in “thin”, “th” as in “then”, “f”, “v”, “s”, “z”, “sh”, “zh” as in “vision”, “h”, and in posh dialects, “wh”),
combining stopping then squeezing (“ch”, “j”), or
narrowing the vocal tract (“w”, “y”, “r”, “l”).
How vowels are produced
All vowel sounds are voiced, unless you’re whispering or speaking Japanese, Quebecois, or a North American indigenous language like Comanche or Cheyenne.
Vowels are sounds produced with the mouth fairly open, and differ by mouth shape, for example “ee” is a high front vowel and “o” as in “got” is a low back vowel.
Some vowels, like the “a” in “cat” and the “i” in “big”, are said with the mouth in the same position from start to finish (monophthongs).
Some vowels, like the “ay” in “paper” and the “I” in “hi”, move from one mouth position to another (diphthongs).
There’s also one vowel in English, the “you” in “human”, which is actually a combination of a consonant and a vowel (“y” + “ooh”). But knowing this doesn’t help us spell it, there isn’t usually any need to notice the little “y” sound, which in some dialects is omitted (think of how the word “news” is pronounced in US English).
Conclusion
Try responding as follows the next time a learner asks you which letters are vowels and which ones are consonants: