The passive periphrastic is a Latin construction that combines a gerundive (the -ndus, -nda, -ndum verbal adjective) with a form of sum to express obligation or necessity, translated "must be" or "has to be," with the person responsible expressed by a dative of agent.
The passive periphrastic is Latin's way of saying something must happen. It has two parts: a gerundive (a verbal adjective ending in -ndus, -nda, -ndum) plus a form of sum. So hoc faciendum est means "this must be done," and the famous Carthago delenda est means "Carthage must be destroyed." The gerundive behaves like any adjective, agreeing with its subject in gender, number, and case, which is why you'll see vitandum (neuter) with a neuter subject but vitanda with a feminine one.
Here's the twist that makes it a test favorite. When Latin wants to say who must do the action, it doesn't use ab + ablative like a normal passive. It uses the dative of agent. Nobis hoc faciendum est literally means "this is to-be-done by us," or more naturally, "we must do this." That double translation (literal vs. smooth) is exactly the move AP Latin translation questions reward.
The passive periphrastic shows up across the entire AP Latin syllabus because both Caesar and Vergil use it constantly. Caesar in particular leans on it when describing military necessity, since everything in the Gallic War seems to be something that must be done right now. The construction sits at the intersection of two skills the course assesses heavily: grammatical analysis (identifying what a form like vitandum is actually doing in a sentence) and literal translation (rendering necessity as "must be" rather than paraphrasing it away). If you can't spot a periphrastic, you'll mistranslate the whole clause, and translation scoring on the exam is segment-by-segment, so one missed construction costs real points.
Keep studying AP Latin Unit SL2Apodi9BqlvQoqDkdk
Adjective Agreement (Units 1-8)
The gerundive is a verbal adjective, so the same agreement rules you learned for ordinary adjectives apply. It must match its subject in gender, number, and case. If you see vitanda with a feminine plural subject, agreement is the clue that tells you they go together.
Ablative Case and Agent (Units 1-8)
Normal passive verbs express the agent with ab plus the ablative. The passive periphrastic breaks that rule and uses the dative of agent instead. This is one of the most-tested case distinctions in the course because it looks wrong until you know the rule.
Ablative Absolute (Units 1-8)
Like the ablative absolute, the passive periphrastic is a compact verbal construction that Latin uses where English would need a whole clause. Both are favorite targets for grammatical-function questions, and both demand a literal translation first before you smooth it into natural English.
Multiple-choice questions love to point at a single gerundive and ask what it's doing. A typical stem reads "In the sentence, vitandum functions as..." and the credited answer identifies it as a gerundive in a passive periphrastic expressing necessity, not a gerund, participle, or supine. On the translation free-response questions, you have to render the construction literally and accurately. "Must be avoided" or "has to be avoided" earns credit; loosely paraphrasing as "they avoided it" does not, because it drops the necessity and the passive voice. Also watch for a dative noun nearby. If you translate it as an indirect object instead of the agent ("by/for whom it must be done"), you'll lose the sense of the clause.
A gerund is a verbal NOUN ("the act of avoiding") that only appears in the singular oblique cases. A gerundive is a verbal ADJECTIVE that agrees with a noun and, when paired with sum, forms the passive periphrastic ("must be avoided"). Quick test: if the -nd- form agrees with a noun or sits next to a form of sum, it's a gerundive. If it stands alone as a noun, it's a gerund. AP multiple choice loves to put both in the answer options for a word like vitandum.
The passive periphrastic is a gerundive (-ndus, -nda, -ndum) plus a form of sum, and it expresses obligation or necessity, translated as "must be" or "has to be."
The person who must do the action goes in the dative case (dative of agent), not the usual ab plus ablative used with normal passive verbs.
The gerundive agrees with its subject in gender, number, and case, just like any other adjective.
On multiple choice, expect questions asking what a form like vitandum "functions as," with gerund, participle, and gerundive all sitting in the answer choices.
On translation questions, you must keep the construction literal: render necessity ("must be avoided"), keep it passive, and translate any dative as the agent.
It's a construction made of a gerundive (the -ndus, -nda, -ndum verbal adjective) plus a form of sum that expresses necessity or obligation. Hoc faciendum est means "this must be done," and the classic example is Carthago delenda est, "Carthage must be destroyed."
No. The gerund is a verbal noun ("avoiding"), while the periphrastic uses a gerundive, a verbal adjective that agrees with a noun. AP multiple choice deliberately offers both as answer choices for forms like vitandum, so check whether the -nd- word agrees with a noun or pairs with sum. If it does, it's a gerundive.
Translate the gerundive plus sum as "must be" or "has to be" plus the verb's meaning, so vitandum est becomes "it must be avoided." If there's a dative noun, that's the agent: nobis vitandum est means "it must be avoided by us," or naturally, "we must avoid it."
That's just the rule for this construction. Normal passive verbs take ab plus ablative for a personal agent, but the periphrastic takes a plain dative, called the dative of agent. Translating that dative as an indirect object instead of the agent is one of the most common errors on translation questions.
Yes. It appears in both Caesar's Gallic War and Vergil's Aeneid, the two required authors. Multiple-choice questions ask you to identify the grammatical function of gerundives like vitandum, and the literal translation free-response questions require you to render the necessity and the dative of agent accurately.