What do the following words have in common?

PET
JET
REAL
SAFE
HEAR
CASUAL

Answers:

Each word can be changed into a new one by adding the letters TY:

PETTY
JETTY
REALTY
SAFETY
HEARTY
CASUALTY

Credit: NY Times Crossword
April 24, 2016
Kathy Wienberg
"TEE" TIME