'Najaf' or 'An Najaf' ?

Factual Questions
1

I’m following along using National Geographic Atlas 7th ed.
It lists the names of cities as follows:
As Nasiriyah
Al Basrah (has Basra in parentheses)
As Samawah
An Najaf
Al Hillah
As Sulaymaniyah
Az Zubayr

I have seen some of these cities named without the preceeding word. Are both correct, or are some U.S. news orgs. a little lazy?

What are the Arabic meanings of Ad, Al, An, As, Ar and Az ?

2

“Al” is Arabic for “the”, and is often prefixed to place names, including cities - perhaps as an honorific. If the “al” comes before the letters S R T N Z L Tz or Sh, the “l” is dropped (that’s just about the only thing I remember from 3 years of highschool Arabic).

3

Sorry - the letter D, too.