Believe it or not, there's no universally agreed upon way to transcribe Mongolian into the Latin alphabet. If you know Mongolian, it's not too much of a problem, as you can figure out what people mean. And many names exist in more or less standard forms. But it still can be very annoying, especially if you are trying to do something like search for a book title in a library catalogue. The Mongolian government decreed a new, official transcription system in late 2003. This actually just confuses things, since they didn't base theirs on one of the more common systems in use. But for what it is worth, you can download it from the link to the left.
Life is further complicated by the fact that Mongolians in various parts of the world use two different alphabets. Officially since the 1940s, and in reality since the 1950s, the Mongolians of the independent country of Mongolia use a form of Cyrillic that has two more letters than the Russian Cyrillic alphabet. The Mongolians of Inner Mongolia (part of China) use a vertical script, usually referred to as 'Mongol bichig' (bichig just means 'writing'). (Read a brief description of it here.) Mongolia started using this again after the democratic revolution of 1990. However, most people are still not very literate in it, and Cyrillic remains the official alphabet.
I will eventually include a section on language and the different alphabets, but until I do, I will note here that the underlying grammar and spelling is NOT identical in the two alphabets. The grammar is more consistent in bichig, but the spelling more closely follows the pronunciation used in Mongolia today in the Cyrillic form. You can 'convert' between the two, but it isn't always intuitively obvious, at least at first.
Some of the letters are transcribed from both bichig and Cyrillic the same way. But this is by no means true for all of them. And even within one alphabet - say, Cyrillic - the transcriptions can vary. What appears in Cyrillic as an 'X' has traditionally been written in the Latin alphabet as 'Kh'. But this is changing. It is now as common, if not more so, to write it as 'H.' But I've also seen it written as 'X' or even 'Q,' depending on who is doing the transcribing.
A similar issue exists when transcribing from the bichig. The letter that is 'X' in Cyrillic is actually two different letters in bichig. This is related to how vowels are classed and treated in Mongolian - there are "male" and "female" vowels (sometimes called "back" and "front" vowels, respectively) - and the 'X' is written slightly differently for each.
All of this goes to explain why you'll find the names of different people, places and terms written differently. Take the word for "people" (usually in the sense of "the people", or "the masses"). It is also often translated incorrectly as "herder." The word from the Cyrillic is easy. It's ard. And any sane transcription system will give you the same result in this case. In bichig, however, the term is arad, which you will also sometimes find written as arat. Thus, the spelling in English (or other Latin alphabet based languages) depends firstly what Mongolian alphabet someone is working from, and secondly on how they are are transcribing it. Nonetheless, you can usually tell what people mean.
AND... All of this does NOT take into account names and words that are more common in English in a corrupted form than in their correct Mongolian form. Genghis, as in Genghis Khan, is one such example. But that will discussion will have to wait for now.Different transcription system
On the left, you can download the official Mongolian government transcription guidelines. You can also download the transcription systems used by the Library of Congress for Mongol bichig and Cyrillic Mongolian. While the transcription they use for Cyrillic Mongolian they use isn't all that common in academic texts, it is useful to have it for finding stuff in on-line catalogues, which do tend to use it. Please note that the Library of Congress Cyrillic transcription is actually for all the non-Slavic languages, so it's a bigger file. (Over 3.5 Mb.) Just scroll down until you reach Mongolian.