Magistra duodecim discipulis fabulam de mari narrat.

Here is the basic breakdown:

• Magistra — the subject: the teacher
• duodecim discipulis — the indirect object: to twelve students
• fabulam — the direct object: a story
• de mari — a prepositional phrase: about the sea
• narrat — the verb: tells / is telling

So the structure is:

The teacher tells a story about the sea to twelve students.

Because magistra is in the nominative singular, which is the case normally used for the subject of a sentence.

A native English speaker may notice that magistra ends in -a, and in Latin that often signals a first-declension nominative singular form.

Also, the verb narrat is third person singular, so it matches a singular subject like magistra.

Because discipulis is an indirect object, not a direct object.

With narrat, Latin often uses:

• the thing being told in the accusative
• the person being told to in the dative

So:

• fabulam = the story being told
• discipulis = the students to whom it is told

If it were discipulos, that would be accusative plural, which would suggest the students were the direct object instead.

Discipulis is dative plural.

Here the dative means to/for the students. Latin often expresses this idea with a case ending instead of a separate word like to.

So English says:

• to the students

Latin says:

• discipulis

without needing a separate word for to.

Because fabulam is the direct object of narrat.

It is the thing being told: a story.

The dictionary form is fabula. In the accusative singular, it becomes fabulam.

So:

• fabula = a story, story
• fabulam = a story, as the direct object

Because the preposition de takes the ablative case.

The noun is mare, maris, meaning sea. Its ablative singular form is mari.

So:

• mare = nominative/accusative singular
• maris = genitive singular
• mari = ablative singular

Since de requires the ablative, Latin uses de mari.

Here de means about or concerning.

So fabulam de mari means:

• a story about the sea

In other contexts, de can also mean things like down from or about/concerning, but here the meaning is clearly about.

Narrat is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from narro, narrare, meaning to tell or to relate.

So narrat means:

• he tells
• she tells
• it tells
• or in context, is telling

Because the subject is magistra, we understand it here as she tells.

Latin usually does not need a subject pronoun if the verb ending already makes the person and number clear.

The ending -t in narrat tells you the verb is third person singular: he/she/it tells.

So Latin can simply say:

• Magistra ... narrat

without adding a separate pronoun like she.

Because duodecim is an indeclinable numeral.

That means it does not change form for case, gender, or number. It stays duodecim.

The noun after it shows the case:

• duodecim discipuli = twelve students
• duodecim discipulis = to/for twelve students
• duodecim discipulos = twelve students as direct object

So the numeral stays the same, while discipulis changes form.

Latin word order is much more flexible than English word order because the case endings show each word’s role.

Putting the verb at the end is very common in Latin, but it is not required.

So this sentence could be rearranged in other ways and still mean basically the same thing, for example:

• Magistra fabulam de mari duodecim discipulis narrat
• Duodecim discipulis magistra fabulam de mari narrat

The endings, not just the position, tell you what each word is doing.

Yes. De mari goes with fabulam and tells you what kind of story it is.

So:

• fabulam = a story
• de mari = about the sea

Together:

• fabulam de mari = a story about the sea

This is similar to English, where about the sea modifies story.

Because Latin has no articles like English the and a/an.

So:

• magistra can mean the teacher or a teacher
• fabulam can mean a story or the story

Context tells you which is more natural in translation.

That is very normal in Latin, and learners have to get used to supplying the or a in English even when Latin does not say them explicitly.