My wife finally replaced her aging Macbook Pro a few weeks ago, and has been making the shift from using Snow Leopard (10.6) to the most recent version of OS X, Mavericks (10.9). One feature that she's been getting used to is autocorrection -- the way OS X will attempt to fix spelling mistakes and typos as you enter text. I find the feature quite useful, but Hanna hates it.
If, like her, you want to turn off autocorrect in Mavericks, you can do so by:
- Open System Preferences, and click on the "Keyboard" icon.
- On the Text tab, uncheck "Correct spelling automatically".
Note that some programs such as Microsoft Office and Mozilla Firefox don't use the system-wide text entry, and you may have to change spelling and grammar settings for those applications individually.