interest

the cost of borrowing money.

"the interest on the national debt alone is abhorrent."

interesting

An overused word which says nothing at all and belittles conversation.

"I'm planning to jump off a building"
"Interesting"

interestation

The action of being thoroughly interested in a topic of choice. Often used in greek mythology.

My interestation in this topic is overwhelming.

Not interested

The dialog option in Final Fantasy 7 when you can't give a fuck

"Hey, do you need instructions on how to ride a Chocobo?"
"Not interested"

Interesting

Oh god, oh god, we're all going to die.

This landing is going to get pretty interesting.

Interesting

Something that actually provokes thought or at least, interest.

That's a really interesting design

interesting

Oh God, oh God, we're all gonna die!

Interesting as defined in "Serenity". (Had to do it ;) )