A boy asks his father to explain the differences among irritation, aggravation, and frustration.

Dad picks up the phone and dials a number at random. When the phone is answered he asks, "Can I speak to Alf, please?"
"No! There's no one called Alf here." The person hangs up.
"That's irritation," says Dad.

He picks up the phone again, dials the same number and asks for Alf a second time.
"No -- there's no one here called Alf. Go away. If you call again I shall telephone the police."
End of conversation.
"That's aggravation."
"Then what's 'frustration'?" asks his son.

The father picks up the phone and dials a third time:
"Hello, this is Alf. Have I received any phone calls?"