Aksa is the tenth letter of the Mandaic alphabet and writes the vowel i as well as the consonant y. It joins only to the right.
It is the third of the three full vowel letters, with halqa and ushenna, and its name is one of the handful in the alphabet that does not follow the a plus sound pattern.
Joined to ad it is read as the syllable di, and that joined pair is the ancestor of dushenna, the separate twenty-third letter, which began life as exactly this ligature and is now written as an undivided sign of its own. Both still exist and do different jobs.
Because aksa joins only to the right, a word containing it is broken into more than one connected run, and those breaks are part of what makes joined Mandaic legible rather than one unbroken stroke. The letters that break a run are halqa, az, it, aksa and ash, together with the three signs that close the alphabet; everything else carries the stroke on.
Aksa holds the tenth place, where yod, yudh and the Arabic letter at ten stand in the neighbouring alphabets, all of which use that letter as a partial indicator of a long i or e. Mandaic made it a vowel outright.
In Hebrew and Syriac the tenth letter carries the numeral value ten and closes the run of units. Mandaic records no numeral use for its letters at all, so aksa marks a place in the sequence and a sound in the language and nothing further, and the correspondence with its cognates stops there.