What do the following words have in common?

STUD
SPUR
LABOR
FACET
VICAR

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

Answer:

Each word can be changed into a new one by adding IOUS at the end:

STUDIOUS
SPURIOUS
LABORIOUS
FACETIOUS
VICARIOUS

Credit:
GAMES/World of Puzzles
September, 2018
DEBT RECKONING