In parvo sinu navis paulisper manet, dum ventus minuitur.

The sentence has:

• a main clause: navis paulisper manet = the ship remains/stays for a little while
• a prepositional phrase: in parvo sinu = in the small bay
• a subordinate clause introduced by dum: dum ventus minuitur = while the wind decreases / dies down

So the overall structure is:

In parvo sinu + navis paulisper manet + dum ventus minuitur

Because navis is nominative singular, which is the case normally used for the subject.

Also:

• manet is 3rd person singular
• navis is a singular noun, so it matches the verb well as the subject

By contrast:

• sinu is ablative singular, not nominative
• it is being used after in, so it belongs to the phrase in parvo sinu

So navis is the thing that manet.

Because Latin word order is much freer than English word order.

English usually needs a more fixed order:

• The ship stays in the small bay

Latin can move words around because the endings show their job in the sentence.

Here, putting in parvo sinu first sets the scene first: in the small bay...

That kind of arrangement is very normal in Latin.

Sinu is ablative singular of sinus, -us.

It is ablative because in takes the ablative when it means in/on in a stationary sense, that is, location.

So:

• in + ablative = in/on somewhere
• in + accusative = into/onto somewhere

Here the ship is not moving into the bay; it is already in the bay, so Latin uses in parvo sinu.

Parvo is the adjective parvus in the ablative singular, agreeing with sinu.

So:

• sinu = bay / curve / fold
• parvo sinu = small bay

Latin adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here both are masculine ablative singular.

Yes. Sinus has a range of meanings related to a curve, fold, or hollow.

Depending on context, it can mean things like:

• a fold of a garment
• a curve
• a gulf or bay

In this sentence, the nautical context makes bay the natural meaning.

Paulisper is an adverb.

It means:

• for a little while
• briefly
• for a short time

It modifies manet, telling us how long the ship stays.

So:

• manet = stays/remains
• paulisper manet = stays for a little while

Here dum means while.

It introduces a subordinate clause describing something happening at the same time as the action of the main clause:

• navis ... manet = the ship stays
• dum ventus minuitur = while the wind decreases

So the two actions are simultaneous.

Both are present indicative.

• manet = he/she/it remains
• minuitur = he/she/it is lessened or decreases

The indicative mood is the normal mood for straightforward statements.

The present tense here gives a simple factual sense: this is what is happening.

Because it is passive in form.

Minuitur is:

• 3rd person singular
• present indicative passive
• from minuo, minuere = to lessen, reduce

So literally it means:

• the wind is lessened
• or the wind is reduced

But in natural English, we often translate it more idiomatically as:

• the wind decreases
• the wind dies down

Latin sometimes uses a passive form where English prefers a different wording.

Yes.

Ventus is nominative singular, so it is the subject of minuitur.

That means:

• ventus = the thing being lessened / decreasing
• minuitur = is lessened / decreases

So inside the dum clause, ventus is the subject.

Because Latin has no articles.

Latin does not have separate words for:

• the
• a/an

So a noun like navis can mean:

• ship
• a ship
• the ship

Which one you choose in English depends on the context.

The same is true for:

• ventus = wind / the wind
• sinu = a bay / the bay

A learner would usually want these forms:

• in = in, on; into, onto
• parvus, -a, -um = small
• sinus, -us (m.) = curve, fold, gulf, bay
• navis, -is (f.) = ship
• paulisper = for a little while
• maneo, manere, mansi, mansum = remain, stay
• dum = while
• ventus, -i (m.) = wind
• minuo, minuere, minui, minutum = lessen, reduce

Knowing the dictionary form helps you recognize why the sentence uses forms like sinu, navis, manet, and minuitur.