Ancient North Arabian is the name given to a group of scripts belonging to the South Semitic script family, which also includes the Ancient South Arabian alphabets (musnad and zabūr) and the vocalized alphabets used in Ethiopia for Geʿez, Amharic, etc.
The Ancient North Arabian scripts were used both in the oases (Dadanitic, Dumaitic, Taymanitic,) and by the nomads (Hismaic, Safaitic, Thamudic B, C, D, and possibly Southern Thamudic). There are tens of thousands of inscriptions and graffiti in these scripts which were used in the period roughly between the sixth century BC and the fourth century AD. See the descriptions of the individual scripts below. You can also see a comparison of the letter forms used in each script in the following table: