The same change can be made to each of the words below to phonetically turn them into other words. 

ON

SIN

MIST 

HEEL

HINT:

The change involves adding two letters at the end of each word that make a one-syllable sound. 

 

Answer:

 

The letters IX can be added to each word to phonetically turn each word into a new one:

 

ONYX

CYNICS

MYSTICS

HELIX

 

Credit:

John Andrew Agpalo