Eihwaz doesn’t have an exact letter correspondence. It is similar to the long vowel “i”

Anglo-Saxon Rune Poem (from ragweedforge.com)

The yew is a tree with rough bark,
hard and fast in the earth, supported by its roots,a guardian of flame and a joy upon an estate

Eihwaz is the rune of the yew tree, the aspect of the Yggdrasil as the tree of the underworld, but also the tree that is connected to all parts of creation. Even though it has a vowel sound, it was rarely used in written inscriptions, it’s sound usually written out long hand in other letters. The bending twisted branches and roots of the yew indicate the many links and connections that it can form, while it’s toxic nature to humans, while being evergreen, and a common tree used in old European cemeteries speaks of it’s connection to the underworld and the afterlife. Sometimes by going down though, one arrives in the upper worlds, and the afterlife can be the means to apotheosis, becoming a divine being.