(Hebrew יחודה) Literally "oneness" or "unity" or "union." From masculine yahid, "the one, the only, the unique" from the verbal root yahad "oneness, union"; cognant with the Hebrew 'ehad, "one."
The highest of the five souls in Kabbalah, corresponding to the sephirah Kether.
"Yehidah is another soul, the fifth. First you incarnate the three souls Nephesh, Ruach and Neshamah and purify them, but the other process of the two other souls Chaiah and Yehidah, they do not incarnate in you, instead, they swallow you. And that is why most of the rituals in ancient times, said that the Lord does not eat garbage, does not eat refuse; it means that we have to purify and to be worthy to be swallowed by God, that is, to be taken as Enoch into heaven. How does this happen? When Yehidah, which is the one, singular, the unique in Hebrew which is that Aleph, Kether, which is symbolized by the eagle—comes and swallows Chaiah." - a lecture about the letter Hei