Ak is the eleventh letter of the Mandaic alphabet and writes k. It joins on both sides.
With the affrication mark beneath it, ak stands for a voiceless velar fricative, the sound in the Scottish pronunciation of loch.
Ak is also the first element of kad, an old ligature of ak and dushenna standing for the word meaning when or as, now written and counted as a single sign. Kad joins only to the right where ak joins on both sides, so the two behave differently on the page despite the shared origin.
The three diacritics of the script, the affrication mark, the vocalization mark and the gemination mark, are all written with the letter rather than beside it, and all three may be omitted from ordinary text. A page of Mandaic therefore records less than the script is capable of recording, and the reader supplies the rest from knowing the word.
Ak holds the eleventh place, where kaph stands in the inherited Aramaic order. In Hebrew and Syriac that letter opens the tens and carries the numeral value twenty. Mandaic records no numeral use for its letters at all, so the eleventh place carries no arithmetic with it here.
Because ak joins on both sides it takes a full set of four shapes and carries a connected run onward, where kad, the sign it helped form, joins only to the right and forces the next letter to start fresh. Two signs with one origin behaving differently on the page is the standing situation with the Mandaic ligature letters.