Declarative speech normally involves a musnad ilayh (what the judgment concerns), a musnad (what is predicated), and isnād (the attribution joining them).
زَيْدٌ عَالِمٌ — Zayd is learned.
Subject of attribution: زَيْدٌ
Predicate: عَالِمٌ
Attribution: affirming learning of Zayd.
The text also introduces complements of verbs. In “كَتَبَ زَيْدٌ الرِّسَالَةَ فِي الْبَيْتِ” the writing is accompanied by an object and a place. These complements receive fuller treatment in the fourth chapter, but their inclusion or omission can already affect what the utterance conveys.