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Latin for Duolingo: 3rd Declension, Lesson 3

Salvete omnes!

This is our third lesson covering the 3rd declension of Latin nouns. For a guide to previous lessons and a classified vocabulary list, be sure to check out these links:
- Directory of Lessons
- Classified Vocabulary List
- Memrise course for vocabulary
- Memrise course with sentences
- Previous lesson: 3rd Declension, Lesson 2

New Grammar

This time, we will introduce the 3rd declension i-stems. These have the reputation of being tricky; in fact, they are listed as #28 in Latin Student Problems on Tumblr. (I just discovered this list recently and have to share it for the benefit of all the Latin geeks on Duo!) So, anyway, back to grammar. We have learned some regular m/f and regular neuter nouns of the 3rd declension in 3 of the cases (and I strongly encourage lots of review of the previous lessons in this declension, since there is so much complexity here). I-stem nouns differ from the regular nouns in having an extra -i- before the ending of the genitive plural. In addition, neuter i-stems have the -i- show up in the nom. and acc. pl., and it is substituted for the -e ending of the abl. s. But there are not very many neuter i-stems in common use, so the most frequent variant you will see is the one in the gen. pl. Clear as mud? Here are the differences highlighted on this chart:

case name | sing. | pl. | typical use
nominative (m./f.) | --- | -es | subject or predicate noun
nominative (n.) | --- | -(i)a | “
genitive | -is | -(i)um | possession, the “of” case
dative | -i | -ibus | indirect object, the “to/for” case
accusative (m.) | -em | -es | direct object (also some objects of preps.)
accusative (n.) | --- | -(i)a | “
ablative | -e | -ibus | objects of prepositions, etc. “by/with/from” case
n. i-stem only | -i | -ibus | “

I-stem nouns have some rules/guidelines that distinguish them from regular 3rd declension nouns, but it might be most helpful just to memorize them as part of your vocabulary study. The vocabulary page will have a model declension for each type of 3rd declension noun. There is also a pretty good survey of 3rd declension nouns at The Latin Library that may help to clarify this for you. All the nouns introduced this lesson will be 3rd declension i-stems, and we will particularly focus on the genitive endings in this lesson (but we’ll look at some of the regular nouns too so you can see the difference.) Also note that there are 3rd declension adjectives (there is a teaser for them at the very end of the sentences this lesson) but I won’t be formally introducing them until later.

New Vocabulary
civis, civis, civium (c.) = citizen
collis, collis, collium (m.) = hill
hostis, hostis, hostium (c.) = enemy
mare, maris, marium (n.) = sea
mons, montis, montium (m.) = mountain
mors, mortis, mortium (f.) = death
nox, noctis, noctium (f.) = night
pars, partis, partium (f.) = part
urbs, urbis, urbium (f.) = city

New Sentences
Civis Romanus/Romana sum. = I am a Roman citizen.
Cives Romae sumus. = We are citizens of Rome.
Cives urbis sunt. = They are citizens of the city.
Cives multarum urbium estis. = You are citizens of many cities.
Est magnum periculum in montibus. = There is great danger in the mountains.
Periculum montium magnum est. = The danger of the mountains is great.
Mors matrum et patrum est mala. = The death of mothers and fathers is bad.
Pars hostium in montibus est. = Part of the enemies is in the mountains.
Virtus civium magna est. = The courage of the citizens is great.
Parvus frater magnum timorem mortis habet. = The little brother has great fear of death.
Amicus matris meae villam in colle habet. = My mother’s friend has a house on a hill.
Collis est altus. = The hill is high.
Roma est urbs collium. = Rome is a city of hills.
Et urbs regum est. = It is also a city of kings.
Mare est altum. = The sea is deep.
Nox est longa. = the night is long.
Terra hostium multos montes habet. = The land of the enemy has many mountains.
A mari usque ad mare. = From sea to sea.
Labor omnia vincit. = Work conquers all.
Omnia amor vincit. = Love conquers all. (Virgil wrote both of these originally. n.b. 3rd declension adjectives are i-stems.)

I think that’s a good introduction to i-stems, although there’s a lot of complexity we haven’t touched yet. We’ll have one more lesson on the 3rd declension, focusing on the dative case, and then I will try to give you some lessons that are more topical (food, family, etc.) and less grammatical. Bonam fortunam!

Go to the next lesson: 3rd Declension, Lesson 4

July 23, 2015



I think it'd be great to make a Latin course on Duolingo. It not only helps with the Romance languages, but the grammar of virtually every Indo-European language to some extent.


I have to disagree with you on the last part. Latin grammar won't help you very much with Persian, Punjabi, or Armenian.


Well Persian and Armenian are the only two agglutinative Indo-European languages. Punjabi is inflected so knowing how to inflect from Latin/any other inflected language would help. Hence "virtually every...to some extent"

[deactivated user]

    I am sure that there are Latin loanwords in Armenian too.


    But yeah, it wouldn't help as much with those, as they are distant relatives. Mostly helps out in Europe while Sanskrit helps in India


    Nice. Please accept a lingot. BTW, you have a sort of rival here at Duo, in Russian..


    Thanks! But hardly a rival, since I couldn't understand any of that post except for the Latin. Won't it be nice when Russian for English speakers is available, and then maybe they can start incubating Latin for English speakers, Latin for Russian speakers, Latin for ...


    Yes, "rival" was not a good choice of words. But it's a fairly interesting intro. The first several lines summarize it:

    So let's begin our acquaintance w/ the Latin language!
    Contents of the lesson:
    1) A brief excursus into the history of the Latin language;
    2) The Latin alphabet and a few peculiarities of reading;
    3) Winged sayings [what the Russians usually call a collection of aphorisms].

    The brief history of the Latin language says nothing you won't know with all your Latin experience, and it emphasizes things medical, since it is taken or paraphrased from a medical Latin textbook. The alphabet section (2) presents the standard Russian pronunciation of Latin, which is a bit different from academic or ecclesiastical, and some tips especially directed at Russian pronunciation. You may find interesting (mildly) the "winged" Latin sayings that were chosen. If you would like a translation of the whole post, I'd be glad to oblige, but you obviously are not in need of an introduction to Latin.

    > Won't it be nice when Russian for English speakers is available, and then maybe they can start incubating Latin . . .

    It definitely will be great. The Russian course in itself should be marvelous, and it may help show the way to present other inflected languages, like Latin, on Duo. Ukrainian is already in beta. I wonder how it goes about presenting all the cases, etc. But I don't want to go through it any time soon, because it is close enough to Russian that I would only confuse the two languages.

    Anyway, thanks for the lessons!

    [deactivated user]

      I was reading the "Latin Student Problems" on Tumbler as I was recovering from a round of the Memrise course and I just realized from whence the "ibus" in « E Pluribus Unum » comes! Thanks!


      Is there any guideline to predict that ars goes artium in the genitive plural?

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