N.B. The email exchange below may have been edited, e.g. to remove content not essential to the main point(s) or to standardize English spelling/grammar.
I'm an amateur screenwriter, and I'm working on a script that utilizes Old Persian. I was surprised to find that there is very little information about this language available ... in bookstores.
The Old Persian word naiba (beautiful, pious)... Is the 'ai' element of this word pronouced like the Modern English word 'eye', or is it pronounced long, like 'they'?
Thanx, M. M.
Re: "...there is very little information about [Old Persian] available on the Internet or in bookstores" --
In books, yes, though not commonly found in bookstores. Some references: Old Persian Texts, Grammars, and Dictionaries.
Re: "Is the 'ai' element of [Old Persian naiba 'beautiful, pious'] pronouced like the Modern English word 'eye', or is it pronounced long, like 'they'?" --
Neither. You can find discussion of reconstructed Old Persian pronunciation on our site [beginning with]: The Old Persian Sound System. Notable is that the 'a' has neither of the sounds you surmise; it's more like 'uh'. And the short 'i' (note absence of macron = long mark) is not pronounced 'ee' but more like 'ih'.
I assume you know that Persians of ca. 600 B.C. did not write in the Roman alphabet; but web publication realities and convenience for scholars dictate standardized transcription [of cuneiform] via Roman script.