- Thank you is defined as an expression of gratitude used to show appreciation for something.
When someone does you a favor and you want to express your gratitude for what they have done, this is an example of a time when you would say thank you.
- The definition of a thank you is an act or expression of gratitude.
When you are grateful to someone for doing you a favor and you bake him a pie to show your appreciation, the pie is an example of a thank you.
(plural thank yous)
- Alternative spelling of thank-you.
Thank you is a shortened expression for I thank you; it is attested since c. 1400.