If you are like most of the average mac user out there, you should normally need no more than 1 – 3 languages installed on your mac. Per default there are a lot more language pack installed for each application on your system. It is possible to free up significant space by removing the unused language data. I do this after each OSX upgrade (major version) because they are delivered with each new realease (e.g. snow leopard, lion, mountain lion). I could regain more than 3GB of disk space with removing the unused languages. You can do it on your own, if you search the web a little and have some scripting skills, but to speed up the process, simple download the open source tool monolingual (click for link) which does the work for you. Simply download the .dmg file, install the package and launch monolingual. At the main app screen
you see a list of all installed languages on your system. Per preset there are some deselected, these ones will reside on your system. Please go through the list and select all languages which have to be deleted and deselect all languages you want to stay on your system. Afterwards hit the remove button in the bottom right corner of the main window. The removal process will take a little to finish depending on how many applications you have installed on your system.