x1 is the principal/chief/main/boss/primary/premier in aspect/organizational principle/role x2 (ka) in organization/system x3.
This is much like tervipsi except that it does not imply the existence of any subordinate/deputy. So the Presidency is an office which may fill x2 in this word or vipsi; here it produces what is normally called the President (x1) but there, it produces the Vice-President. This allows for abbreviations such as "(A)(V)P(E)otUS", but brings symmetry between VP and P, allowing also for strings with variable characters which allow the referent to range over the possibilities (offices) more easily (rather than reminding people that a null character is possible), such as with "XPotUS", wherein "X" is variable and thus the string can refer to the PotUS or the VPotUs (and possibly those with "A" concatenated to their fronts).