setmice fu'ivla

x1 is a set (mathematical) consisting of elements x2, x3, x4, etc.

See setmima, ce, porsice, gunmace, menrece


In notes:

gunmace
x1 is a mass/group consisting of elements x2, x3, x4, etc.
menrece
x1 is among x2, x3, x4, etc.
porsice
x1 is an ordered sequence consisting of elements x2, x3, x4, etc.