How To Find the Declension of Any Latin Noun
Confused about Latin noun declensions? Then read this quick post to learn how to find the declension of any Latin noun.
Latin has five noun declensions (or groups of nouns that share the same case endings). Each and every Latin noun belongs to one of these five declensions, and it is crucial that you be able to determine which declension.
In this post, I’ll tell you
- why you need to know a Latin noun’s declension
- how to tell what declension any Latin noun is part of
Let’s get started!
Why does a noun’s declension matter?
Noun declensions are an important part of Latin. If you don’t know a noun’s declension, you will not be able to understand how it fits into a sentence.
Why not? Well, because different declensions have different case endings – and sometimes those case endings can look similar or even identical.
For instance, 2nd declension genitive singular (-ī) can be confused with 3rd declension i-stem ablative singular (also –ī). Yikes!
And if you are looking at a text that does not use macrons, then the possibilities for misidentification multiply. –is could be –is (3rd declension genitive singular) or –īs (1st and 2nd declension dative and ablative plural). Etc.
I am not saying all this to scare you, but rather to emphasize my point: knowing a noun’s declension is crucial. If you know what declension a noun belongs to, you will be able to correctly identify its grammatical case.
And then you will be able to determine how the noun relates to the rest of the words in its sentence. This, ultimately, is what will allow you to understand Latin.
Now that we have that cleared up, let’s move on to the process itself: identifying a noun’s declension.
How To Find the Declension of A Latin Noun
As I mentioned above, Latin has five declensions: first, second, third, fourth, and fifth. But, you ask, how do you tell what declension a Latin noun belongs to? Well, you are in luck.
It is actually super easy to identify the declension of a Latin noun. You look at the noun’s genitive singular form and see what ending it has. This ending tells you which declension it belongs to.
Here are the genitive singular endings for the different declensions:
| Declension | Genitive Singular |
|---|---|
| First | -ae |
| Second | -ī |
| Third | -is |
| Fourth | -ūs |
| Fifth | -eī / ēī |
Okay, let’s test it out by looking at an example.
mater, matris
I have given this noun in dictionary entry style, which means first its nominative singular and then its genitive singular. So we need to look at the second form to determine the declension.
Matris ends in -is, which is the ending of the third declension. We have found our declension! See? Super easy.
Now you try! What declension does each of the following nouns belong to?
- mōns, montis
- exercitus, exercitūs
- verbum, verbī
- iter, itineris
- sella, sellae
- rēs, reī
- mūrus, mūrī
- agricola, agricolae
- 3rd
- 4th
- 2nd
- 3rd
- 1st
- 5th
- 2nd
- 1st
Okay, that wasn’t too bad, was it? You just have to memorize the five genitive singular endings, and then you can tell what declension any noun belongs to.
(Wondering what the genitive case does? We have been talking about it a lot. You can read about the genitive next.)
How To Tell A Noun’s Declension From The Dictionary
When you look up a noun in a Latin dictionary, you will be given the nominative singular and the genitive singular (in that order). Sometimes the genitive singular is abbreviated, but the important point is this: the genitive singular ending will always be visible.
(You can confirm this by playing around with Logeion, my favorite online Latin dictionary.)
Remember: when you look up a noun in the dictionary, look at the second form to tell what declension it is.
Time for an example. I have created an infographic featuring the dictionary entry for lūmen. There is a lot of information in even this short excerpt, but you can see that the (abbreviated) genitive singular remains in second place.
Although the genitive has been abbreviated, you can still see the final -is. This means that this noun belongs to – pop quiz – what declension?
(If you answered “third”, good job! -is is the genitive singular ending of the third declension, so lūmen is a third declension noun.)
We just have a little bit more to cover in this post. But first, if this has been helpful, make sure you sign up for my Latin-themed email list. You will get a printable declension cheat sheet and 2 worksheets . . . as well as lots of invaluable tips in your inbox.
How To Find the Declension of Plural-Only Latin Nouns
In the post title, I said I would tell you how to find the declension of any Latin noun. And I meant that! So it’s time to talk about plural-only nouns (pluralia tantum)- nouns that don’t have a singular form.
We have these nouns in English, too. Scissors, pliers, pants . . . the list goes on. In Latin, there are quite a few of them.
Now obviously if the noun is plural-only, you can’t look at the genitive singular to determine its declension. So, instead, you look at the genitive plural. Logical, right?
Here are the genitive plural endings for the five declensions:
| Declension | Genitive Plural |
|---|---|
| First | -ārum |
| Second | -ōrum |
| Third | -um / ium |
| Fourth | -uum |
| Fifth | -ērum |
When you see a plural-only noun in your dictionary or textbook, you still look at the second form to tell what declension it is. But it will be the genitive plural, not the genitive singular.
You can practice with the following exercise:
- moenia, ium
- Quinquātrūs, uum
- angustiae, ārum
- arma, ōrum
- 3rd
- 4th
- 1st
- 2nd
Final Thoughts
Congratulations! Now you know how to find the declension of any Latin noun. All you need is a textbook or dictionary to give you the noun’s genitive singular (or plural, in the case of plural-only nouns).
PRO TIP: You can speed up the process even more by memorizing a noun’s genitive singular when you memorize its definition. I always put each noun’s genitive singular on my Latin flashcards, and I highly recommend that you do, too.
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The information is amazing. Great logical structure.
I only have a minor problem with the seizure-inducing pink.
Haha this comment made me laugh. I’m glad you find the information helpful! You are in luck with regard to the pink, because I am currently in the process of redoing the colors and the pink will be changing to purple.
Oh SO incredibly helpful. Thank you! I’ve been watching online Latin Lectures and these posts are so helpful for the questions I have that the lecturer didn’t answer. lol Thanks again! 🙂
You are very welcome, Monica, and thank you for your kind words! The goal for this site is to answer the questions that tend to fall through the cracks, so it’s great to know my posts are helping 🙂
As a PhD candidate in Hebrew Bible, I occasionally need to “dip into” Latin for a few terms here and there. I find this site very helpful. Thank you, Livia!
I am happy to be able to help, Daniel! Hebrew is on my learning list for some day – so far my only experience with a Semitic language has been Akkadian.
Absolutely fantastic post. Thank you. There are a few broken links, however.
I’m glad the post was helpful, Taylor! Thank you so much for letting me know about the broken links – they should be fixed now.
In an exam, without a dictionary to tell you the genetive singular, is there anyway you can work out the declension of a noun? Thanks!
Hi Felix, if you don’t know the genitive singular, things become much harder, and sometimes it is impossible to know the declension for sure. But here is my advice:
1. Look at the case ending on the noun. Some case endings are only found in certain declensions. Ae, am, ārum, and ās only show up in the first declension, while ō, ōrum, and ōs only belong to the second declension. E / ē and ēs can be either third or fifth declension, but fifth declension nouns are much rarer so this ending likely signals third declension.
The problem is that many endings can appear in multiple declensions. For example, -a could be a first declension noun in the nominative (or ablative, if macrons aren’t marked), but it could also be a neuter noun of the second, third, or fourth declension in the nominative/accusative plural. -um could be accusative singular of the second or fourth declension (+ nominative singular neuter of the second) OR genitive plural of third declension.
2. Once you have used the ending to narrow down your options, look at the overall context of the sentence. What case would make sense? If you have a noun ending in -um, check to see if the logic of the sentence requires an accusative, nominative, or genitive.
This is really all you can do if you don’t have access to a dictionary. I know it is frustrating on exams if there is new vocabulary, but try to focus on what you know about the sentence and then fill in the gaps in your knowledge by guesswork.
Why is there not an example of a 5th declension pluralia tantum noun?
The answer is that I honestly cannot think of one and I haven’t been able to find one in my research, either. There aren’t as many 5th declension nouns in Latin in general, so it wouldn’t surprise me if pluralia tantum nouns simply didn’t exist in that declension.
If you or anyone else knows of an example, I can add it!
Great work! Please keep it up and keep it simple as you have done here. Thanks.
Thanks for stopping by, Peter! My goal is to explain everything as clearly and simply as possible!