Ruach · רוח — the breath that goes up and downרוח

Wind, breath, spirit — the same word for all three, and the ambiguity is not sloppiness. Bereshit Rabbah defines it by its motion: ruach is the one that goes up and comes down, citing Ecclesiastes 3:21.

⭐ Which means the middle soul is defined as a direction of travel rather than a substance — the only one of the five that is described by what it does instead of what it is. This app already has that rhythm as its own node: ratzo va-shov, running and returning.

It is the moral and emotional register — the part that wants things, and can want them well or badly. In the sefirotic reading it is not one sephirah but six: the whole heart-range from Chesed down to Yesod, which is why every one of those six carries ruach in its own entry with a different shade beside it. In the Lurianic reading it comes from Yetzirah, the world of formation.