Amnis celeriter fluit.

Because amnis is a third-declension noun. In Latin, the subject is usually in the nominative case, but nominative singular endings are not all the same.

A learner often first meets nouns like:

• puella = girl
• servus = slave

so it is easy to expect the subject to end in -a or -us. But third-declension nouns often have different nominative forms. Here, amnis is the nominative singular, so it can correctly be the subject of the sentence.

Celeriter is an adverb. It tells you how the river flows: quickly.

So the sentence breaks down like this:

• amnis = river
• celeriter = quickly
• fluit = flows

Because celer is an adjective, while celeriter is an adverb.

• celer means quick or swift
• celeriter means quickly or swiftly

In this sentence, the word modifies the verb fluit, not the noun amnis. Since it describes the action of flowing, Latin uses the adverb celeriter.

If you wanted to describe the river itself as swift, you could say something like amnis celer = the river is swift.

Fluit is:

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

It comes from the verb fluere, meaning to flow.

So fluit means he/she/it flows or simply flows. Since the subject is amnis (river), the natural translation is the river flows.

Latin normally has no definite article and no indefinite article.

So:

• amnis can mean river, a river, or the river

The correct English choice depends on context. In a simple teaching sentence like this, the river is often the most natural translation, but Latin itself does not separately mark the.

Yes. Latin word order is much more flexible than English word order because Latin uses word endings to show grammatical function.

So all of these could be understood similarly:

• Amnis celeriter fluit
• Celeriter amnis fluit
• Amnis fluit celeriter

The most neutral English translation is still The river flows quickly.

That said, changing the order can slightly change emphasis. For example, putting celeriter first may emphasize the speed.

Because Latin verbs already show the person and number in their endings.

The ending -t in fluit tells you it is third person singular: he/she/it flows.

So Latin often does not need an explicit subject pronoun unless the speaker wants extra emphasis or contrast.

Here, amnis is already stated as the subject, so no separate it is needed.

Here it is intransitive. That means it does not take a direct object.

In Amnis celeriter fluit, the river is simply performing the action of flowing. Nothing is being acted upon directly.

So the structure is:

• subject: amnis
• adverb: celeriter
• verb: fluit

There is no direct object.

Amnis is in the nominative singular.

We know this because it is the subject of the verb fluit. The thing doing the action of flowing is the river, so the noun must be in the nominative.

This is a useful habit in Latin: when you see a finite verb like fluit, ask who or what is doing the action? The answer here is amnis.

A common classroom pronunciation is roughly:

AHM-nis keh-LEH-ri-ter FLOO-it

A few details:

• amnis: the a is like a in father
• celeriter: hard c sound, like k
• fluit: usually pronounced in separate parts, roughly floo-it

If you are using restored classical pronunciation, that is a good approximation.

It can mean either, depending on context.

Latin present tense often covers both:

• the river flows
• the river is flowing

In a short standalone sentence like this, English usually chooses flows quickly, especially if the sentence is just giving a simple fact. But is flowing quickly could also be correct in the right context.

The pattern is:

noun + adverb + verb

More specifically:

• amnis = subject
• celeriter = adverb modifying the verb
• fluit = verb

So it is a very simple Latin sentence showing a complete thought: The river flows quickly.