والمركب ما يقصد بجزئه الدلالة على جزء معناه
A compound expression is one whose constituent part is intended to signify a part of its total intended meaning.
In “ghulāmu Zaydin” (Zayd's servant), each element contributes to the relational meaning, so the expression is compound.
In “Zaydun qāʾimun” (Zayd is standing), the subject and predicate also contribute separately; it is compound as well. Yet only the latter makes a complete assertion, showing that compounding and completeness of judgment are different issues.