The Forms of Latin's Fifth Declension

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Latin is an inflected language and the endings of words change as they indicate their meaning and usage in a sentence. Each Latin noun belongs to one of five declensions, with its own set of endings, forms, and irregularities. To translate Latin with any competency, memorizing the gender, the genitive form, and the endings of each declension is key.

The fifth declension is the last of the five declensions. By the time students encounter the fifth declension, they are usually in the intermediate stage of elementary Latin and are fully aware of its irregularities and exceptions to rules. The fifth declension proves no different.

Most fifth declension nouns are feminine with a few exceptions. This is similar to the first declension, in which most nouns are feminine with a few masculine irregularities. There are no neuter fifth declension nouns, making it one of the easier declensions to learn, a reprieve from previous struggles with Latin declensions.

Fifth Declension Forms

One of the most common nouns in Latin is found in the fifth declension. Res (thing) is where English gets republic (res publica): literally public thing. In fact, thing is a generic translation because res has so many translations when coupled with other words. Res is declined as follows:


nom. Res

gen. Rei

dat. Rei

acc. Rem

abl. Re


nom. Res

gen. Rerum

dat. Rebus

acc. Res

abl. Rebus

There are a few issues with the declining of Res that give students trouble. First, the form Res is found in the nominative singular and both the nominative and accusative plural. However, similar forms have been encountered in previous declensions, most notably neuter singular nouns of the fourth declension. The genitive and dative singular have similar forms just like those of the first declension. Context and occasionally word order will reveal which case should be used in translation. Finally, notice the recurring –um of the genitive plural, like previous declensions. Although, here in the fifth declension, the ending is changed to –erum. Also note the similarity in the dative and ablative plural (–ebus) to the forms of the third and fourth declension (–ibus).


The fifth declension should present to the elementary student little trouble in comparison to previous declensions. At this stage of a student’s study, memorization of the gender, genitive singular, and endings of a declension should be second nature and automatic. Luckily, the fifth declension provides few irregularities with its straight-forward constructions and similar case endings to previous declensions.

This post is part of the series: Latin Declensions

Since Latin is an inflected language, the endings of its words change to indicate their function in a sentence. Latin nouns and adjectives are declined into five basic cases. These nouns and adjectives belong to one of five declensions, each with its own set of rules and forms.

  1. How to Decline First Declension Latin Nouns
  2. A Primer on Latin’s Second Declension
  3. Learn How to Form Third Declension Latin Nouns
  4. Latin Declensions: Fourth Declension
  5. How to Decline Latin Words of the Fifth Declension