sumka'i lujvo

x1 is a pro-sumti/pronoun representing x2 as argument of predicate/function x3 filling place x4.

See also sumti, krati

In notes:

brika'i
x1 is a pro-bridi representing predicate relationship x2 with relation x3 among arguments x4.
goilka'i
x1 (text / virtual-text-object) is a variable representing x2