All intents and purposes. And intensive purposes.

Until I was about twenty years old, I thought that the phrase "all intents and purposes" was "all intensive purposes."

And while I heard people say the phrase quite often, I never used it myself, simply because no purpose seemed so intensive as to describe it using this extreme a word. 

I can recall wondering on more than one occasion why so many people considered so many things so damn intensive, especially when the situations to which they were referencing were anything but intensive.

I can also remember feeling catastrophically stupid but also incredibly relieved at discovering the true meaning of the phrase.  

The world had suddenly become slightly less emotional. 

Any similar misunderstandings you'd like to share?