Another fundamental distinction is between the head or start and the end, and between upper and lower, as the proposition goes on to say:
...some are higher and others lower. Things can be higher or lower in terms of their proximity to the root or the extent to which they spread in relation to the lower world. This is the “measure of the height” (שיעור הקומה, shiur hakomah): every upper level has a higher function than the level below it. These concepts enable us to understand the developmental sequence governing the emergence of the Partzufim and also how the lights are connected with one another.