A bit of background. I do not want to give the wrong impression, I am by no means fluent in Arabic. I studied it for a couple of years in college and have some basic knowledge. If I practice real hard every day, I can hold a very small conversation for a limited period. I am a little better at reading and writing it than speaking it, but probably about the level of competency that most people have in Spanish when they take it in high school. So my grasp of the language is quite basic. Still it has been beneficial to me in studying history, in gaming and in trying to learn bits of other languages. This is one area where it has been especially handy.
Before getting into sun and moon letters, I need to talk about the definite article in Arabic: "al-"(ال). This is made by combing the letters alif (ا) and the lam (ل). Because it is a cursive script, Arabic letters change form depending on their position so when you put alif and lam together in front of the word 'king' (ملك) they look like this: الملك
Most of the time, "al-" means "the". However it can also be used to mean something like the preposition "of". This is called the idafa and it usually occurs by placing the definite article (al) before the noun in question. For example to "the sword of the king" is written as "sword the king" or سيف الملك
I am sure a lot of readers have seen the definite article all the time in news articles and history books. For example you've probably read stories about Al-Shabaab and you've probably heard of Al-Jazeera. Al-Shabaab just means "The Youth" while Al Jazeera means "The Peninsula". Sometimes there is a hyphen and sometimes not. It doesn't really matter but the hyphen indicates that "al" is connected to the word it precedes in Arabic.
|This chart by Gaspard is a handy reference|
to Sun and Moon letters
Sun letters appear in red
Sun and Moon letters are important categories in Arabic based on how they sound. As a general rule Sun letters are pronounced with the teeth and consist of letters like: t, th, d, s, sh, dh, etc. Moon letters are usually pronounced toward the back of the mouth or with the lips: q, k, m, b, etc. These are generalizations but they are a useful guide. The rule of Sun and Moon letters is anytime a sun letter follows "al" you do not pronounce the lam (or "l") in "al" but instead double up the sound of the sun letter. So Al-Shabaab, becomes Ash-Shabaab. To use another example, al-sayf becomes as-sayf; and al-tarik becomes at-tarik. To use an example in gaming the setting Al-Qadim would be pronounced as it is spelled because Q is a moon letter (the letter qaf or ق).
Sometimes people simply opt to spell it how it sounds when they romanize the letters. This is not the standard, but I think it is a lot less confusing and prefer it. It is the approach we took in Gamandria for that reason. So Al-Tarja appears as At-Tarja in the book because that is how I pronounce it. We also got around this issue by making the definite article in most dialects of Khubsi (our mash of Arabic, Phoenician and Hebrew) "alu-" instead of "al-". That way the sun and moon letter pronunciations never arise.