In the English language, almost all words contain a combination of vowels and consonants.  Assuredly, you can identify the vowels, but you may not appreciate how the vowels differ from consonants.  The distinction relates to how the vowels are spoken — with the mouth open!  A consonant sound involves a full or partial block of air through the mouth.  If the tongue or lips touch anything, the letter is a consonant.  Its that simple!  Just try to utter a consonant without blocking some air flow from your mouth, however slight.  

Now that we have established the difference between vowels and consonants, lets consider whether the English language utilizes any all-vowel or all-consonant words?  

First, identify any all-consonant words.  I made a list of candidate utterances, and then checked them in my dictionary, a 1,960 page tome. (The Random House Dictionary, unabridged edition) I found one:  “Shh,” defined as “Hush!  Be still,” although some may argue for inclusion of a few more standards, like:  Psst, Pfft, Brrr or Awrk.  In addition, Some comic book character balloons utilize symbols, like #$%&@, simulating curse words, but those do not count.     

Second, name any all-vowel words.  English incorporates five full time vowels:  A, E, I O, U, and one part time vowel, Y.  Of the ten most common letters in English usage; namely, E. T, A, O, I N, S, H, R, D (letterfrequency.org), four are vowels. The vowel “U” stands in 13th place  and the “Y,” much further down the line.   How many words can you identify that contain all vowels?  No consonants need apply.  I can list six: 

— Eau: The French word for “water,” and frequently used to describe perfumes, as in eau of cologne. It uses only three letters, all vowels, and pronounced as a fourth vowel “o.” — a four bagger!  

— Aye:  A three vowel English word for “yes,” mostly used in nautical or parliamentary settings, and is also pronounced as a fourth vowel, “I.”

— Eye:  Another English three vowel word, pronounced like a fourth vowel, “I” 

— You:  A three vowel word pronounced like one of them, “U”

— Oiu:  The french word for “yes” contains three vowels, and is pronounced as “wi”

— Yea:  Another English word for “yes.”

Admittedly, eau and oui could be challenged as predominantly foreign language words, but they have been used sufficiently in the English language to become familiar.  And lets not forget the notorious “Old Macdonald’s Farm” lyric, known to all:  EIEIO, clearly sung with the mouth open.  Ooo-eee.!