There are 3 in your question!
Stretch is a 7 letter word with e as the only vowel. Twelfth is another 7 letter words containing only one vowel.
Rhythm = contains six letters and the only vowel in this word is the "y".
The word strength has only one vowel.The adopted word from German, schnapps, also has only one vowel.
angst
Strengths
stir
The "i" is the only vowel in "which", and it has a short vowel sound.
The letter A (the only vowel) has a short A sound.
Stretch is a 7 letter word with e as the only vowel. Twelfth is another 7 letter words containing only one vowel.
evil
Rhythm = contains six letters and the only vowel in this word is the "y".
"Strengths" is a 9-letter word with only one vowel.
The word strength has only one vowel.The adopted word from German, schnapps, also has only one vowel.
If you are referring to the verb "fish", than one possible option would be Cast.
angst
alumatomexamitem
Yes, in this word, Y is a vowel. Y is the only letter that can be both a consonant or a vowel. When it makes an E sound, it is a vowel.