Multilingual Dictionary Database question
If it were my decision, it would look like this:

words (wordID, word, languageID, date_of_addition)
related_words (wordID, otherword0
definitions (wordID, definition, order)
languages (languageID, languageName, languageIdentifier)
language_name_translations (languageID, languageTranslatedID, 
                            languageTranslatedName)
  So that this table can be joined back on the previous one to use the two ids 
  to show for instance that 2 (spanish) is presented to users of 1 (english) as 
  "Espanol" (really it's just because this is _my_ definition that it makes sense
  to me, you would work on your own definitions of course)
synonyms (wordID1, wordID2)
antonyms (wordID1, wordID2)
word_origins (originID, wordID1, wordID2, notes)


So I would suggest at this point that you go get a copy of OED and identify all the parts that they present in their listings. Find out things like related words and word origins and consider that every single entry is a list in some fashion or another, so every presented part should be an entity in a table.