Apt

apt , likely : Words sometimes misapplied. Apt implies natural fitness or tendency; likely applies to a contingent event considered as very probable.

Apt, Likely, Liable.Apt  means quick  or skillful. “He is apt to learn,” means that he learns readily. “He is likely to learn,” means that he will probably learn. “He is liable to learn,” is incorrect. Liable for  means responsible for; liable to  means subject to. “He is liable for the entire sum, and liable to imprisonment if he does not pay.”