Genitive with Adjectives
A small, closed list of Latin adjectives demands a genitive where English uses a preposition. Cupidus glōriae, "greedy for glory"; perītus iūris, "skilled in law"; memor vestrī, "mindful of you." The genitive names the thing the adjective points at — what is desired, known, remembered, shared, full or empty.
Memorize the AP-tested set — desire, knowledge, memory, sharing, fullness, likeness — and the construction parses itself. The trap is similis: it slides between genitive and dative, and editors disagree about which to print.
The other is plēnus, which prefers the ablative in classical prose even though A&G lists it here.
The genitive names the thing the adjective points at — "greedy for…," "skilled in…," "mindful of…."
Plēnus often takes ablative in classical prose; similis slides between genitive and dative — see ConfusionGuard.
See It In Action
— Sall. Cat. xxviii. 4
Cupidam (acc. fem. agreeing with plebem) takes novārum rērum in the objective genitive — literally "desirous of new things," the standard Latin idiom for political upheaval. The genitive names the object of the desire.
— Sall. Cat. xvii. 7
Ignārus ("unaware") sits in the knowledge family of A&G § 349. a — it points at what someone does or doesn't know, and the genitive names the thing known. The litotes nōn ignārum is Sallust's quiet way of accusing Crassus without saying so outright.
— Sall. Cat. lx. 3
Memor always takes a genitive — there is no dative alternative. Notice how Sallust wedges prīstinae virtūtis between veterānī and memorēs: the adjective and its genitive are bonded, even when other words come between them.
Similis is the one closed-list adjective that takes BOTH genitive and dative. Classical prose mostly uses dative; fixed phrases and poetry keep the genitive.
fixed comparisons, poetic register, things rather than persons
vērī similis
like the truth → "plausible"
classical prose default — comparisons to a specific person
patrī similis
like his father
Tip: Ask: am I comparing to a person or living thing? Use the dative (Cicero, Caesar). Am I in a fixed phrase (vērī similis) or in poetry? The genitive is at home there. On a quiz, both can be correct — read the source.
In Sallust's veterānī prīstinae virtūtis memorēs comminus instāre (Cat. lx. 3), why is prīstinae virtūtis in the genitive?
Study Tips
- •Memorize the closed list as four families — desire (cupidus, studiōsus), knowledge (perītus, gnārus, ignārus), memory (memor, immemor), sharing/fullness/likeness (particeps, expers, plēnus, inānis, similis). Four columns, twelve words.
- •When you see one of these adjectives, look immediately for a genitive — it is almost always the next word or the next phrase, even when separated by line breaks in poetry.
- •Similis is the asterisk: classical prose mostly uses dative for living things (patrī similis, "like his father") and genitive for fixed comparisons (vērī similis, "like the truth" → "plausible"). Don't pick a side on a quiz without checking the noun.