Iah

The term jꜥḥ literally means "Moon" in Egyptian and functions both as the ordinary noun for the lunar body and as its divine personification in Egyptian cosmology. Iah appears in Middle Kingdom texts as an early lunar god; over time the deity's identity and functions were merged with other gods connected to the moon, knowledge, and the afterlife.

In the sources Iah is described as a human figure, portrayed as a young man described as having skin "as fair and white as milk." Iconographically he is shown wearing lunar emblems — a disk and crescent — on his head; his costume can resemble that of Khonsu but he is usually depicted wearing a full wig rather than the child's sidelock used for Khonsu, and occasionally an Atef crown topped by an additional symbol.

As the personified Moon, Iah embodies the lunar cycle and its monthly renewal; this cyclical aspect is linked in sources to themes of rebirth and the dead through later assimilation with Osiris. Iah was associated with the god Thoth and in the compound Iah-Djehuty served as a lunar aspect of Thoth. The moon's visible segments were also used as fractional symbols in Egyptian writing, a connection noted in discussions of Iah's associations with calculation and measurement when linked to Thoth. The sources describe identification and functional overlap with Khonsu and Thoth rather than listing active magical powers.