The difference between Ability and Aptitude

When used as nouns, ability means suitableness, whereas aptitude means natural ability to acquire knowledge or skill.

check bellow for the other definitions of Ability and Aptitude

Ability as a noun (obsolete):

Suitableness.
Ability as a noun (uncountable):

The quality or state of being able; capacity to do or of doing something; having the necessary power.

Examples:

"This phone has the ability to have its software upgraded wirelessly."

"This wood has the ability to fight off insects, fungus, and mold for a considerable time."
Ability as a noun:

The legal wherewithal to act.
Ability as a noun (now, limited to, _, Scottish, _, dialects):

Physical power.
Ability as a noun (archaic):

Financial ability.
Ability as a noun (uncountable):

A unique power of the mind; a faculty.
Ability as a noun (countable):

A skill or competence in doing; mental power; talent; aptitude.

Examples:

"They are persons of ability, who will go far in life."

"She has an uncanny ability to defuse conflict."