placed before a selbri, merges x1 and x2 places.
Causes relabelling so that all slots which were originally subsequent to x2 have their indices decremented by 1; therefore, for example, the original x3 is the new x2. Notice that "se'e'i se'e'i" merges the original x1, x2, and x3 slots all together; likewise, under "se se'e'i", the new x1 is the original x3 and the new x2 is the original x1 and x2 mutually merged together (therefore, "se'e'i" is equivalent to "se'e'i se" but not "se se'e'i"). See also: "te'e'i", "ve'e'i", "xe'e'i", te'e'a, ze'e'au.