1) The Hebrew word "OSSIOT" (Letters) אותיות represents vessels. The twenty-two letters comprise the entire construction of the "Partzuf".
In other words, just as the twenty-two letters, which are expressed through the medium of writing, embrace all the wisdom in the world; for, through the combinations of the twenty-two letters, it is possible to explain every branch of wisdom or science in the world. The same can be said with regard to the vessels of the "Partzuf". The vessels have the power of receiving light and, in turn, of bestowing the affluence of all the lights by means of the combinations and unions brought about through the instrumentality of the vessels that abide in the "Partzuf".
The combinations and unions that occur in the Sephiroth can be likened to the manifold combinations of the letters of the Hebrew alphabet. We also count twenty-seven letters to the Hebrew alphabet, arriving at that number only when we attempt to analyze the meaning of "M.N". It is the curtain which blocks the passage of the light. This accounts for the coarseness predominant in the twenty-two letters. The Hebrew alphabet then takes on five additional letters and, as a result, the alphabet becomes increased to twenty-seven letters.
These letters are recognized as the five final letters known as םןץףך "M.N.Z.P.CH.". The coarseness inherent in the letters, which is a barrier to the light, actually constitutes the power that forges the boundary and terminating point, which restricts the upper light from passing through. In other words, it is the power that restrains the light from entering the curtain which is spread out upon the "M.N.Z.P.CH.". It is because of this condition existing between the light and the curtains of the five letters that a clash union takes place between them. Therefore, a returning light is the result of the collision between the light and the barrier; that is to say: The revelation of the returning horizontal light that ascends from below upwards is a light which draws the upper vertical light and robes it.
It follows then that the five letters םןץףך "M.N.Z.P.CH." are the source that causes to spring into existence the twenty-two letters so that all of the vessels, that is, the twenty- two letters, in and of themselves, are but an extension of the curtain, meaning that it was the clash union that caused the ten Sephiroth to manifest.