Lesson 46 · Review
Nine of these twelve words are fourth-declension nouns, and all nine are military — the vocabulary of an army on the march.
A noun of this declension is listed, as always, by its nominative and genitive — and here the genitive is printed as the bare ending -ūs because it is the same for every noun in the declension, masculine and neuter alike. When you see -ūs in a vocabulary entry, you are looking at a fourth-declension noun and need read no further.
Two idioms come with the vocabulary. impetum facere in, with the accusative, is the regular way to say make an attack on — the attack is the object made, and the thing attacked follows in. And cornū, a horn, is also the wing of an army: ā dextrō cornū, on the right wing; ā sinistrō cornū, on the left wing.
exercitus, an army · equitātus, its cavalry · impetus, its attack · adventus, its arrival · cornū, its wing
The whole declension is described by two rules and one short list of exceptions.
Nouns of the fourth declension are either masculine or neuter. There is no regular feminine.
Masculine nouns end in -us, neuters in -ū. The genitive ends in -ūs.
Only the last of these three identifies the declension by itself. A nominative in -us is shared with the second declension — amīcus, servus, equus all end so — and no amount of staring at exercitus will tell you which home it belongs to. The genitive settles it at once: amīcī is second declension, exercitūs is fourth.
amīcus, amīcī — second · exercitus, exercitūs — fourth
A few nouns of this declension are feminine against the rule, and they must simply be learned: domus, house, and manus, hand, are the two you will meet constantly. Their forms are perfectly regular — it is only their gender that departs, and it departs where it matters, in the adjectives that must agree with them: manus mea, my hand, never manus meus.
One masculine model and one neuter, and the neuter is the shorter story of the two.
Masculine · adventus, -ūs, arrival · stem adventu- · base advent-
| Singular | Terminations | Plural | Terminations | |
|---|---|---|---|---|
| Nom. | adventus | -us | adventūs | -ūs |
| Gen. | adventūs | -ūs | adventuum | -uum |
| Dat. | adventuī (-ū) | -uī (-ū) | adventibus | -ibus |
| Acc. | adventum | -um | adventūs | -ūs |
| Abl. | adventū | -ū | adventibus | -ibus |
Neuter · cornū, -ūs, horn, wing · stem cornu- · base corn-
| Singular | Terminations | Plural | Terminations | |
|---|---|---|---|---|
| Nom. | cornū | -ū | cornua | -ua |
| Gen. | cornūs | -ūs | cornuum | -uum |
| Dat. | cornū | -ū | cornibus | -ibus |
| Acc. | cornū | -ū | cornua | -ua |
| Abl. | cornū | -ū | cornibus | -ibus |
The base is found here exactly as in the other declensions: drop the ending of the genitive singular. adventūs → advent-; cornūs → corn-; exercitūs → exercit-. The stem is the base plus the declension's characteristic vowel, u — which is why the u is audible in nearly every form and why this declension is also called the u-declension.
Four observations that turn the two tables above into a habit of the eye.
In the singular, cornū is the form for four cases out of five — nominative, accusative, dative, and ablative. Only the genitive cornūs stands apart. The neuter law you already know (nominative and accusative always alike) is here extended almost to the whole singular, and the case must be read off the sentence, not the word: ā dextrō cornū is ablative because ā takes the ablative, not because the ending says so.
cornū is also the only neuter of this declension in common use — learn it and you have learned them all.
The masculine noun spends -ūs three times over: it is the genitive singular, the nominative plural, and the accusative plural. Nothing in the word chooses among them; the sentence does.
tempus adventūs — the time of the arrival (gen. sg.) · post adventūs — after the arrivals (acc. pl., because post takes the accusative)
The same warning applies to the pair adventus and adventūs, which differ by one mark of quantity. In writing the macron decides the case; in speech the length of the vowel does.
lacus, lake, has -ubus in the dative and ablative plural — lacubus, not lacibus. portus, harbor, allows either: portubus or portibus. Every other noun in your vocabulary takes the regular -ibus.
ante, before, and post, after or behind, both govern the accusative. They pair naturally with the new nouns: ante adventum, before the arrival; post proelium, after the battle. Note that adventum is the accusative singular — the -um looks second-declension, but the genitive adventūs tells the truth.
Six out of six before you start the exercises.
Question 1
Which single form tells you that a noun belongs to the fourth declension?
Right. Rule 2 gives three endings, but only the genitive is exclusive. A nominative in -us is shared with the second declension (amīcus, servus), so option a cannot decide anything; -ibus in the plural is shared with the third declension (mīlitibus, lēgibus), so option c cannot either. exercitūs against amīcī settles the question in one glance — which is exactly why the vocabulary prints the genitive.
Not quite — ask of each ending whether some other declension also uses it. Only one of the three belongs to the fourth declension alone.
Question 2
In the singular of the neuter cornū, how many of the five cases are the bare form cornū?
Right. The neuter law guarantees the nominative and accusative will match, but this declension goes further and gives the dative and ablative the same -ū as well. Only cornūs, the genitive, stands out. The consequence for reading is that the case of cornū is never legible in the word itself: in ā dextrō cornū it is ablative because ā demands the ablative, and in cornua vīdit the plural cornua is accusative because it is what he saw.
Not quite — run down the neuter singular column of the paradigm and count the cells that read cornū. Then check which one does not.
Question 3
You meet adventūs in a sentence. Which cases can it be?
Right. The masculine paradigm spends -ūs three times: genitive singular, nominative plural, accusative plural. Nothing in the form chooses among them, so you read the governing word first — a preposition, a verb, or another noun that wants a genitive. Option b invents a second-declension plural this noun does not have; option c ignores the macron, which is precisely what separates the nominative singular adventus (short u) from the three long-ū forms.
Not quite — find every cell in the masculine paradigm that reads adventūs. There is more than one, and they are not all singular.
Question 4
What is the dative and ablative plural of lacus, lake?
Right. lacus and portus are the two small irregularities of the declension: lacubus is required, portubus and portibus are both correct, and everything else in your vocabulary takes the regular -ibus of option a. Option b names a real form, but the wrong one — lacuum is the genitive plural, on the pattern of adventuum and cornuum.
Not quite — the lesson singles out two nouns whose dative and ablative plural refuse the regular ending. This is one of them.
Question 5
Rule 1 says fourth-declension nouns are masculine or neuter. Where do domus, house, and manus, hand, fit?
Right. A handful of nouns of this declension — domus and manus the commonest — are feminine against the rule, and there is nothing to do but learn them. They decline exactly like adventus: manus, manūs, manuī, manum, manū. The exception costs you nothing until an adjective has to agree, and then it costs everything: manus mea, my hand, and never manus meus — which is what option c would produce.
Not quite — check the genitive the vocabulary prints for manus. Then ask what an exception to a rule about gender can and cannot change about the endings.
Question 6
How does Latin say they made an attack on the camp?
Right. The idiom is impetum facere in with the accusative: the attack is the thing made, so impetum is the direct object, and the thing attacked follows the preposition in — here in castra. Option b makes the camp a possessor, an attack belonging to the camp, which reverses the sense. Option c puts the attack in the ablative and the camp in the object slot, so that they are making a camp by means of an attack.
Not quite — the vocabulary entry for impetus prints the idiom in full, including which case follows in. Ask which word is the thing being made.
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