Iah was sometimes considered an adult form of Khonsu and was increasingly absorbed by him.

He differed in usually wearing a full wig instead of a child's sidelock, and sometimes the Atef topped by another symbol.

[4] As time went on, Iah also became Iah-Djehuty, meaning "god of the new moon".

[5] In this role, he assumed the lunar aspect of Thoth (also known as Djehuty), who was the god of knowledge, writing and calculation.

[6] Iah was also assimilated with Osiris, god of the dead, perhaps because, in its monthly cycle, the Moon appears to renew itself.