A duck's quack doesn't echo, and no one knows why.

The "save" icon on Microsoft Word shows a floppy disk, with the
shutter on backwards.

The combination "ough" can be pronounced in nine different ways.
The following sentence contains them all: "A rough-coated,
dough-faced, thoughtful plough man strode through the streets of
Scarborough; after falling into a slough, he coughed and
hiccoughed."

"The verb "cleave" is the only English word with two synonyms
which are antonyms of each other: adhere and separate.

The only 15 letter word that can be spelled without repeating a
letter is uncopyrightable.

Facetious and abstemious contain all the vowels in the correct
order, as does arsenious, meaning "containing arsenic."