The kesuba (marriage contract) is written in a smattering of Hebrew with Aramaic thrown in. It is possible that onr or both parties may not know what all the words in the kesuba mean. Furthermore it promises vague amounts of money, which many men may not realize the current market value of. At some weddings I have seen a Rav broadly outline the meaning of the document, but usually only to the husband only.
If this is a legal document why don't we write it in the language that the parties both speak? Is the document valid if one or both parties don't really understand what is in it?