What is "iou"

I O U \I O U\, IOU \I.O.U\([imac]" [=o]" [=u]"). [phonetic, from I owe you.] A paper having on it these letters, with a sum named, and duly signed; -- in use in England as an acknowledgment of a debt, and taken as evidence thereof, but not amounting to a promissory note; a due bill.
--Wharton.
--Story.

An IOU is an acknowledgment of debt.

IOU may also refer to:

In music:

• I.O.U. (album), by jazz fusion guitarist Allan Holdsworth
• "I.O.U." (Freeez song), by jazz-funk group Freeez
• "I.O.U." (Jimmy Dean song), by country singer Jimmy Dean
• "I.O.U." (Lee Greenwood song)
• I.O.U. (hip-hop group), an American hip-hop duo
• I.O.U., a 1989 album by Gregory Isaacs

In organizations:

• Investor-owned utility, a supplier of basic services
• Intercultural Open University Foundation, a distance education institution
• Islamic Online University, an online, distance-learning university founded by Bilal Philips
• International Ornithologists' Union, new name of the International Ornithological Committee

In other uses:

• Interdependent Occupational Unit, the monetary unit of the Kingdom of Lovely in the British television series How to Start Your Own Country
• The acronym for the fictional Illuminati University in the Eponymous GURPS book. (No one knows what the 'O' stands for, except maybe the Arch Dean.)

An IOU (abbreviated from the phrase "I owe you") is usually an informal document acknowledging debt. An IOU differs from a promissory note in that an IOU is not a negotiable instrument and does not specify repayment terms such as the time of repayment. IOUs usually specify the debtor, the amount owed, and sometimes the creditor. IOUs may be signed or carry distinguishing marks or designs to ensure authenticity. In some cases, IOUs may be redeemable for a specific product or service rather than a quantity of currency, constituting a form of scrip.