What do the following words have in common?

FIN
PAR
VAN
SPAN
FLOUR

HINT: The same three letters will change each word into a new one.

Answer:

The letters ISH can be added to the end of each word to form new words:

FINISH
PARISH
VANISH
SPANISH
FLOURISH

Credit: LA Times Crossword
Sylvia Bursztyn and Barry Tunick
KINDA SORTA