Choosing Dictionary.app spelling language I'm Venezuelan, so my native language is Spanish. But I have my MacMini and my MacBook in English because that's the way I like to work, it's better for my (and my job). Usually, when I access Dictionary app (mostly with Alfred), I can just look out the definitions, synonyms and whatnot in English, but not in Spanish.

The only way I know how to switch the language is changing the global language settings (via System Preferences > Language and Text). This means that the whole OS would be in Spanish. I would like to be able to use both languages in Dictionary.app, at the same time, so I can look out definitions, synonyms, and else in both languages (specially through Alfred).

Any way I can achieve that?
The Dictionary.app supplied by Apple only has English and Japanese, regardless of what language you set your OS to.  You can add modules as explained here:

http://m10lmac.blogspot.com/2011/12/more-dictionaries-for-dictionaryapp.html

Dictionary.app has nothing to do with spellchecking, that is done by other parts of the OS.  You can change the spellcheck to Spanish in Apple apps by going to Edit > Spelling and Grammary > Show Spelling and Grammar.