Transliteration of Arabic into English is not a perfect art - many place names will have multiple spellings in circulation making life a little difficult.
We received some clarification from a native Arabic speaker who is also fluent in English regarding 'harrat' - lavafields, over which many of the prehistoric stone built structures such as kites, pendants and wheels are built. The follow advice we hope you will also find informative and useful.
If you are talking about one lavafield it is harra (singular).
Two or more is harrat (plural). (Harrat Khaybar would mean the lavafields (plural) of Khaybar).
Used in conjunction with a specific name it becomes Harret - The great lavafield sprawling across northeast Jordan and into its neighbours is Harret al-Shaam. In Jordan they commonly simply refer to it as Al-Harra.