Remex in rate sedet et funem solvit, dum portitor pueros monet ne ad alveum propius accedant.

Because in can take either the ablative or the accusative, depending on the meaning.

• in + ablative = in/on something, showing location
• in + accusative = into/onto something, showing movement toward

Here, rate is the ablative singular of ratis (raft, boat), and in rate means on the raft or in the boat.

So:

• in rate sedet = he is sitting on the raft
• if it were movement, you might get something like in ratem ascendit = he climbed onto the raft

Remex is a noun in the nominative singular. It means rower or oarsman.

Since it is nominative singular, it is the subject of the verbs sedet and solvit:

• remex ... sedet = the rower sits
• remex ... solvit = the rower loosens/unties the rope

Latin often uses one subject with two verbs, just as English can.

Because funem is the direct object of solvit.

• solvo means I loosen, I release, I untie
• the thing being loosened or untied goes into the accusative

So:

• funis = rope, cord
• funem = the rope

Thus funem solvit means he unties the rope or he loosens the rope.

Both are present indicative active, third person singular:

• sedet = he/she sits or is sitting
• solvit = he/she loosens/unties or is untying

Latin present tense often covers both a simple present and a progressive present in English. So either of these may work depending on context:

• the rower sits and unties the rope
• the rower is sitting on the raft and untying the rope

Here dum means while.

In Latin, dum is often followed by the present indicative when it means while, even if English might translate it more flexibly. So:

• dum portitor pueros monet = while the ferryman warns the boys

The verb monet is present indicative, third person singular.

This is a very common construction:

• dum
  • present indicative = while ...

The subject of monet is portitor.

• portitor is nominative singular
• monet is third person singular

So portitor pueros monet means the ferryman warns the boys.

Then pueros is the direct object of monet.

Because moneo normally takes a direct object in the accusative: you warn someone.

So:

• pueri = the boys
• pueros = the boys, as object

Therefore:

• portitor pueros monet = the ferryman warns the boys

Latin is doing exactly what English does here: the person being warned is the object.

Because after verbs like moneo (warn), Latin often uses ne + subjunctive for a negative command/warning.

So:

• monet ne ... accedant = he warns them not to approach ...

This is a very common pattern:

• moneo aliquem ne + subjunctive
• I warn someone not to ...

So ne here means that ... not or more naturally in English not to.

Because it is part of the clause introduced by ne after monet.

This is an example of a subordinate clause of indirect command (or a warning expressed in that pattern):

• portitor pueros monet ne ... accedant
• the ferryman warns the boys not to approach ...

Accedant is:

• present subjunctive
• third person plural

It is plural because it refers to the boys.

So Latin is not saying they actually do approach; it is expressing what they are being warned not to do.

Because its understood subject is pueri/pueros — the boys.

Even though pueros is accusative in the main clause, it still supplies the logical subject of the subordinate clause:

• portitor pueros monet ne ... accedant
• the ferryman warns the boys that they should not approach

Since they = the boys, the verb is third person plural:

• accedant = they may approach / should approach with ne = they should not approach

Propius here is an adverb, meaning more closely, nearer, or simply too near in context.

It does not agree with alveum because it is not an adjective here. It modifies the verb accedant:

• ad alveum propius accedant = approach nearer to the channel/bed

A very literal sense would be:

• that they should not come nearer to the channel

English often translates more naturally as:

• not to go too close to the stream/channel

Because accedo means approach, come near, and it can be used with ad + accusative to show what someone approaches.

So:

• ad alveum accedant = they approach the channel/riverbed/stream

Alveum is the accusative singular of alveus.

This is a normal way to express motion toward something:

• ad
  • accusative = toward, to

Alveum is the accusative singular of alveus.

Depending on context, alveus can mean things like:

• channel
• riverbed
• stream-bed
• sometimes trough or hollow

In this sentence, since the ferryman is warning the boys not to come too near, it probably refers to the water channel or riverbed/stream edge.

So learners should mainly notice two things:

• it is a noun
• it is in the accusative because of ad

It is fairly natural Latin word order, though Latin is more flexible than English.

The sentence is:

Remex in rate sedet et funem solvit, dum portitor pueros monet ne ad alveum propius accedant.

A more English-like order would be:

• The rower sits on the raft and unties the rope, while the ferryman warns the boys not to go nearer to the channel.

Latin often places words in an order that highlights important ideas or sounds balanced, rather than following a fixed subject-verb-object pattern.

A few things to notice:

• remex comes early, introducing the subject
• in rate is placed near sedet
• funem comes before solvit, which is common
• the warning clause puts ne before the verb it governs, as expected

So the word order may feel different from English, but nothing here is strange by Latin standards.

Yes. Solvo has a range of meanings, including:

• loosen
• release
• untie
• set free

In this sentence, because the object is funem (rope), the natural meaning is unties or loosens.

So funem solvit could be understood as:

• he unties the rope
• he loosens the rope

The exact English wording depends on context, but the grammar stays the same.