ID:278472
 
For instance, say I I translated "bdmn" from an abjad text, does that mean any vowels can be appended to those letters?
Apparently people argue about which way is the right way to say something in an ancient language, and they'll be as close as "Badaman" and "Bedemen" (Kind of like how people say Muhammad, mohamed, mahamad, etc...).

Or does it mean that there's certain vowels, but we just can't know? (Because there are no longer any speakers who speak the exact same ancient language, lets just say)
When Anglicizing text, adding vowels is appropriate. It's not so much that vowels didn't exist in ancient languages, but that they often weren't considered important enough to write down. This of course is a grievous oversight, which can be forgiven only on the basis that writing was kind of a new thing then. In many ancient texts, since the space was not a convention yet you can also have different divisions of words that change the meaning of the text (which could in some cases be deliberate, like a pun).
In response to Lummox JR
Right, but does it matter which vowels?

I understand if the vowels aren't added, in English it'll sound like you're trying to make a bow-tie with your tongue, but when you do pronounce it, does it matter what vowels?
In response to Ill Im
Typically the vowels won't precisely correspond to English equivalents, but there is often a convention for such things. That is, there's usually a spelling that's preferred. The best thing is to stick with what's closest in the original pronunciation if you're not sure.

As an example of convention, the Japanese word pronounced "des" is written as "desu" in the Roman alphabet because that's a literal translation from the Kanji spelling of the word. (I only know this because my cousin studied Japanese in college.)