liable, likely, apt

Although these words are largely interchangeable when used to express probability, each of them has a specific primary meaning.

Apt means “naturally inclined” or “suitable.”

• Ginger, the cat, is apt (inclined) to run away if the door is left open.
• For a freelance editor, a thesaurus is an apt (suitable) gift.

Liable means “answerable” or “likely” (especially with some risk of an unpleasant outcome). It should not be used in a positive context.

• Criminals are liable for their actions.
• People who drink and drive are liable to cause an accident.

Likely means “expected” or “probable.” For most situations, likely is the best choice.

• We are likely (or liable) to be late for the concert if this heavy rain continues.
• Shanta is likely (not liable) to get the highest marks in her class again this year.