WHAT IS A NOUN?
A noun is a word that indicates an object: a person, place, or thing. It can be a cow, an airplane, a shoe, dishwashing liquid, a storm, the TARDIS, a walrus, courage, a banana, truth, happiness, or Tom Hiddleston. In English, most nouns look and work the same, no matter where or how you put them in a sentence.
The house is blue. Lightning struck the house. Jupiter is angry at the people in the house.
The house is blue. Lightning struck the house. Jupiter is angry at the people in the house.
HOW DO NOUNS WORK IN LATIN?
In the above example sentences, the house is the subject of the first sentence (the thing doing the action), the direct object of the second sentence (the thing receiving the action), and the object of a preposition (a phrase describing how or where the action takes place) in the third sentence. In each situation, the word house does not change its spelling, only where it is positioned in the sentence. The reason I'm pointing this out is that in Latin, the spelling of the word DOES change based on what function it serves in the sentence. The word house in Latin is domus. Watch how it changes as we translate those English example sentences into Latin.
domus est caerulea. fulmen domum pulsavit. Iuppiter irascitur hominibus in domo.
Notice the word changed the spelling of its ending based on its function, or use, in the sentence. Almost all Latin nouns, with just a very rare few exceptions, do this. So how do you know what letters will change, when they will change, and how they will change?
There are two important concepts to know here: case and declension.
The case of a noun is what it looks like and how it operates in its specific role in the sentence. In the Latin example sentences above, when domus changed to domum and then domo, what changed is its case. That's why the spelling is different for each version of the word. There are six different cases for each noun:
(Click on the name of each case for an in-depth explanation of what it means.)
The other important thing to know about a noun is its declension. Declensions are categories that we put nouns in to help us understand how their cases work. As a general rule, all nouns in a declension share the same endings for all their cases. For example, domus is in the same declension as servus. When you put domus in the accusative case, it becomes domum; when you put servus in the accusative case, it becomes servum. Notice that their nominative cases both end in "-us" and their accusative cases both end in "-um." If you were to put these two words in all the other cases, you'd find that all their other cases have the same endings as well. This is why we put them in a declension, or noun category, together.
domus est caerulea. fulmen domum pulsavit. Iuppiter irascitur hominibus in domo.
Notice the word changed the spelling of its ending based on its function, or use, in the sentence. Almost all Latin nouns, with just a very rare few exceptions, do this. So how do you know what letters will change, when they will change, and how they will change?
There are two important concepts to know here: case and declension.
The case of a noun is what it looks like and how it operates in its specific role in the sentence. In the Latin example sentences above, when domus changed to domum and then domo, what changed is its case. That's why the spelling is different for each version of the word. There are six different cases for each noun:
(Click on the name of each case for an in-depth explanation of what it means.)
The other important thing to know about a noun is its declension. Declensions are categories that we put nouns in to help us understand how their cases work. As a general rule, all nouns in a declension share the same endings for all their cases. For example, domus is in the same declension as servus. When you put domus in the accusative case, it becomes domum; when you put servus in the accusative case, it becomes servum. Notice that their nominative cases both end in "-us" and their accusative cases both end in "-um." If you were to put these two words in all the other cases, you'd find that all their other cases have the same endings as well. This is why we put them in a declension, or noun category, together.
PRINCIPAL PARTS OF A NOUN (AND HOW TO FIND ITS DECLENSION)
Before we get into the different declensions, let's talk about what it looks like when you first look up a Latin word in a dictionary. To do that, let's look up the word domus.
domus, domī, f.
In a typical Latin dictionary, you are given the word's three principal parts.
The first principal part is the nominative singular form of the noun. This is typically seen as the "normal" form of the noun; it's probably the one you are learning when you learn a new noun for a vocabulary quiz.
The second principal part is the genitive singular form of the noun - more on what that means on the genitive case page. The important thing to know here is that the genitive ending (in the case of domus, the -ī on the end of domī) is what determines the declension that this noun belongs to.
The third principal part is the gender of the noun. All nouns in Latin have a gender - masculine, feminine, or neuter, represented by m, f, or n. More on gender when we talk about adjectives.
Let's go back to the second principal part for a second, the genitive, to talk about declensions. Like I said, almost all Latin nouns belong to a declension, a group of words that all behave in a similar way grammatically. Those groups are separated from one another and categorized according to the letters at the end of their genitive case - the second principal part. There are five declensions in all. Here are the genitive endings for each declension.
1st Declension 2nd Declension 3rd Declension 4th Declension 5th Declension
-ae -ī -is -ū -ēī
So domus, domī, f. belongs to the 2nd declension, but femina, feminae, f. belongs to the 1st declension, and rēs, rēī, n. belongs to the 5th declension. Got it? Good.
domus, domī, f.
In a typical Latin dictionary, you are given the word's three principal parts.
The first principal part is the nominative singular form of the noun. This is typically seen as the "normal" form of the noun; it's probably the one you are learning when you learn a new noun for a vocabulary quiz.
The second principal part is the genitive singular form of the noun - more on what that means on the genitive case page. The important thing to know here is that the genitive ending (in the case of domus, the -ī on the end of domī) is what determines the declension that this noun belongs to.
The third principal part is the gender of the noun. All nouns in Latin have a gender - masculine, feminine, or neuter, represented by m, f, or n. More on gender when we talk about adjectives.
Let's go back to the second principal part for a second, the genitive, to talk about declensions. Like I said, almost all Latin nouns belong to a declension, a group of words that all behave in a similar way grammatically. Those groups are separated from one another and categorized according to the letters at the end of their genitive case - the second principal part. There are five declensions in all. Here are the genitive endings for each declension.
1st Declension 2nd Declension 3rd Declension 4th Declension 5th Declension
-ae -ī -is -ū -ēī
So domus, domī, f. belongs to the 2nd declension, but femina, feminae, f. belongs to the 1st declension, and rēs, rēī, n. belongs to the 5th declension. Got it? Good.
HOW TO WRITE LATIN NOUNS
Here are the basic rules for how to write any Latin noun in whatever case and number you want. The "1PP" and "2PP" are just abbreviations for "first principal part" and "second principal part," respectively.
