How to Form Latin Adjectives of the Third Declension

Group One Latin adjectives consist of adjectives from both the first and second declension. These adjectives function identically to those of English. However, since Latin is an inflected language, their forms in sentences bear no resemblance to their English counterparts. Typically, a Latin adjective follows the noun it modifies. To explain this, many Latin programs tell the student to think of it this way: A noun is more important than an adjective that modifies or characterizes it. This is why a noun comes before an adjective in Latin. This contrasts to English, in which adjectives normally appear before the nouns they modify.

Group Two adjectives consist only of adjectives of the third declension. This fact is deceptively simple in contrast to Group One adjectives, which consist of adjectives from the two previous declension. This deception derives from the fact that Group Two adjectives break down further into three subcategories. If there were ever a time to emphasize the need to memorize all the forms of an adjective, this would be it. Identifying to which subcategory an adjective belongs depends on how many nominative singular case forms it has. To some Latin students, the need to memorize the forms of Group One adjectives seems unnecessary as they follow regular patterns with a few exceptions. However, this practice in the early part of a student’s study makes it much easier for a student to learn Group Two adjectives.

The most common subcategory of Group Two adjectives are those known as two-form adjectives. They are so called because they have only two nominative forms; one for masculine and feminine forms and one for the neuter form. In other words, two-form adjectives share the same nominative singular form for both masculine and feminine adjectives and there is a separate nominative singular form for neuter adjectives. The Latin word “fortis” is an example of a two-form adjective. Its declension looks like this:

Singular

nom. fortis, forte

gen. fortis, fortis

dat. forti, forti

acc. fortem, forte

abl. forti, forti

Plural

nom. fortes, fortia

gen. fortium, fortium

dat. fortibus, fortibus

acc. fortes, fortia

abl. fortibus, fortibus

Notice that since the masculine and feminine genders have the same form, it is unnecessary to repeat them. The neuter form of the adjective, with its separate nominative singular form, is declined fully above.

The second most common Group Two adjectives are those of the one-form variety. They are called one-form adjectives because all three genders share the same form throughout the nominative singular case. The word “potens” is an example of a one-form adjective. Its declension looks like this:

Singular

nom. potens, potens

gen. potentis, potentis

dat. potenti, potenti

acc. potentem, potens

abl. potenti, potenti

Plural

nom. potentes, potentia

gen. potentium, potentium

dat. potentibus, potentibus

acc. potentes, potentia

abl. potentibus, potentibus

Notice that the masculine, feminine, and neuter nominative case all have the characteristic similar nominative singular form of a one-form adjective.

Not surprisingly, three-form adjectives have three separate forms in the nominative singular for each of the three genders. These adjectives are the least common of the Group Two adjectives. The word “acer” is an example of a three-form adjective. Its declension looks like this:

Singular

nom. acer, acris, acre

gen. acris, acris, acris

dat. acri, acri, acri

acc. acrem, acrem, acre

abl. acri, acri, acri

Plural

nom. acres, acres, acria

gen. acrium, acrium, acrium

dat. acribus, acribus, acribus

acc. acres, acres, acria

abl. acribus, acribus, acribus

Notice that there is a separate nominative singular form for each of the three genders characteristic of three-form adjectives.

Although Group Two adjectives consist of adjectives from only the third declension, their three subcategories make them far more complicated than those adjectives of Group One. The key to identifying whether a Group Two adjective is of the one-, two, or three-form variety is in the number of nominative singular forms it has. Notice that although the word “potens” is a two-form adjective, it still takes two columns to decline it fully; it needs one column for the masculine and feminine forms and a separate column for the neuter forms. A Group Two adjective belongs to a subcategory because of its number of nominative singular forms only, not because of the number of columns needed to decline it fully. This fact gives students trouble when they expect Group Two adjectives to behave like those of Group One.