A three letter word that ends in the letter x could be the word Hex. A hex is a witches curse or spell.
Latex is a 5 letter word. It begins with L and ends with X.
mim
xylophone
miter box
oxeye
No, there is no word in the English language that starts and ends with the letter "x."
Texter
Unfix is a 5 letter word. It begins with U and ends with X.
anthrax
appendix.
phlox
Latex is a 5 letter word. It begins with L and ends with X.
x-raying
SUSSEX
index
suffix
PARADOX