What do all of the four-letter words below have in common?

FAIR
FORT
GRIM
PART
PAST
READ
WEAR

HINT:
They can all be changed into new words in the same way.

Answer:

Each word becomes a new one when Y is added at the end.

Credit:
GAMES/World of Puzzles
May, 2018
Scott Erdman
WORDS TO THE WISE