Kad is a sign of the Mandaic alphabet that began as a ligature of ak and dushenna, written for the word meaning when, or as, or like. As dushenna did, it hardened into a letter used as an undivided whole, and it is usually written on its own.
It joins only to the right, where ak, the letter it grew out of, joins on both sides, so the two behave differently on the page despite their shared origin. Dushenna, its other element, is itself a hardened ligature, which makes kad a ligature built on a ligature.
Kad falls outside the traditional count of twenty-four, which runs from halqa to at, adds dushenna, and then closes by writing halqa a second time. The modern character standard encodes twenty-five Mandaic letters, more than the traditional reckoning names, because it has to serve editions of manuscripts as well as the count the tradition itself keeps.
This atlas holds an entry for kad for the same reason a standard encodes it: the sign exists, it appears in writing, and a reader meeting it needs somewhere to look it up. Where it stands in the tradition's own reckoning is recorded on the entry rather than assumed.
Because kad joins only to the right, whatever follows it begins a fresh connected group. It is usually written on its own, standing for the whole word it was made to represent, so a reader meets it as a unit rather than as a letter inside a spelling. That is an unusual thing for anything counted among the signs of an alphabet.