sumdai lujvo

x1 is an object (may or may not be material); any object that can be the subject of a noun or sumti; "object" in object-oriented programming

See sumti. Differs from dacti in that it need not be physical or material; also includes things like nu-events, du'u-propositions, etc.

In notes:

x1 (mass) is the object type of argument object x2, as defined by property x3 (ka)