a. The Accusative of the Direct Object denotes (1) that which is directly affected, or (2) that which is caused or produced by the action of the verb: -
NOTE: There is no definite line by which transitive verbs can be distinguished from intransitive. Verbs which usually take a direct object (expressed or implied) are called transitive, but many of these are often used intransitively or absolutely. Thus timeó, I fear, is transitive in the sentence inimícum timeó, I fear my enemy, but intransitive (absolute) in nólí timére, don't be afraid. Again, many verbs are transative in one sense and intransitive in another: as, - Helvétiós superáverunt Romání, the Romans overcame the Helvetians; but nihil superábat, nothing remained (was left over). So also many verbs commonly intransitive may be used transitively with a slight change of meaning: as, - rídés, you are laughing; but mé rídés, you're laughing at me.
b. The object of a transitive verb in the active voice becomes its subject in the passive, and is put in the nominative (§275):