Add more info about passive
Object is one of dependent parts of sentence, but often is required for certain verbs of predicate. Object is always an argument of predicate. While object is usually treated as receiver of action (patient) made by subject (agent), the roles of object and subject may be swapped in passive constructions.
There may be more than zero or one objects in the sentence. Then one of them is called direct and other are indirect. Example:
Uruk thrakuzû nazgum durubûr (takob) = Orcs brought the ring for/to (their) ruler.
Where “nazgum” (the ring) is the direct object and “durubûr” (to ruler) is the indirect object. Please note, that pronominal phrase “takob” is a modifier here, not an object.
Object may include optional modifier (usually an adjective): “I have a beautiful ring” ⇒ “Dabrus ash nazgnîr”.
Noun related to verb is not always an object (or subject). Only nouns in grammatical cases (Accusative/Objective, Genitive, Dative) are objects. Noun in locative or marginal case is usually an adverbial. Genitive case with possessive function forms an adjectival phrase from noun or pronoun.