The page will eventually serve as a launching page for this topic.
Multilingual is a term that defines usage that contains more than one language. This might be a book with two languages face to face on adjacent pages or it might be used to describe a live audio translator. It could also be used to define an OCR tool with multi-alphabet recognition. It might also mean that an book is available in more than one language. Lots of people who write books would like to see their book available in additional languages but currently this is an expensive thing to do, costing something like 17 cents a word. The question is: Is there a cheaper way, using technology? Is computer aided translation up to the task? If not then what can be done to make it better? The answers seem to be: It depends.
 Types of Multilingual books
 Mixed Books
The section cover the case where there are multiple languages used in the one book. This kind of book was very popular back in the 18th and 19th centuries. The reader is expected to have some ability to understand several languages or at least some forms of popular words in other languages. Often the second language in these books is Latin since some popular quotes were from the Latin and it was also used in some churches. You are most likely to encounter a book like this if you frequent older books, perhaps with the idea of creating an eBook.
Of course there are also mixed language books created in the 20th and 21st centuries as well. This are often reference works but even fiction books might use a different language in a dialog spoken by a character.
Sometimes the best way to handle a book like this is to follow the original language with a paragraph in the primary language (here called English). The idea is that your target reader will have a handy reference translation. Since Latin is often used here it is nice that Google has a Latin translator available. For this application a machine translation may be just fine. Other choices include placing the information in a footnote or just hope your reader can muddle through it, or perhaps it is just a quote or saying and it doesn't impact the story itself.
Other mixed books simply have a word or two in a foreign language. Here a simple translation dictionary may be adequate. The translation can be inserted in parens or with lead in text that is inline with the main text itself. A second way is to provide a footnote or endnote.
 Dual Book
A dual book with a single book translated to a second language and then placed inside the same book. Generally these kinds of books have one language on odd page numbers and a second language for the same text on even page numbers resulting in a parallel book. These are often used by someone trying to learn a new language. These work well for paper books but can be problematic for eBooks.
It would be possible to make an FXL book with facing pages in different languages but then the reader would likely need to have a dual page display capability to match the paper book. Another technique would be to use a table with two columns, one for each language. They can be kept in sync using a new table row every once in a while. The table itself can be invisible if desired. This may or may not work well with a given reader. Building a new table often can help with getting it to work properly. Other possibilities would include alternating paragraphs.
Aglona Reader is a program designed to create and read dual books as parallel books. It defines a special format for this use.
 Several Books
Two or more independent books where all are translations of the original. Each book is actually a separate edition and is often not a parallel translation. It is often thought of as the same story told in a different language. The translation is independently copyrighted as it is really a rewrite.
There is no requirement that the format of the books remain the same in different languages. One popular use is audio books which could be in a different language than the written book. Some technologies exist to be able to keep the two copies in sync.
 Multilingual books available
- Interlinear Books -- features bilingual books for language learners translated in the Interlinear format, where the translation follows each word or phrase. Available in ePub, PDF formats. Currently serves Swedish, German, Lithuanian and Russian books.
- Doppeltext -- features Bilingual books - for ePub 3, Kindle, and web browsers. They use professional published translation. Click a paragraph to see it translated in the flow or set up parallel flows.