noun
IOU
noun
1
An informal written note acknowledging a debt, from the phrase "I owe you."
"He scribbled an IOU on a napkin and promised to pay her back Friday."
How to Use IOU
Learner’s notesIn plain EnglishA casual note promising to repay money owed.
Common pairings
write an IOU
settle an IOU
Word Forms
IOUs plural
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Etymology
From the pronunciation of the phrase "I owe you," first recorded in this shorthand form in the early 17th century.