Laŭ la leĝo, la posedanto devas ripari la kaldronon.

Laŭ is a preposition meaning according to, in accordance with, or sometimes based on.

In Laŭ la leĝo, it means according to the law.

A useful thing to remember is that prepositions in Esperanto normally do not change form, and laŭ is always followed by a noun phrase without -n just because of the preposition itself:

• laŭ la reguloj = according to the rules
• laŭ mi = according to me / in my opinion

La is the Esperanto definite article, equivalent to English the.

So:

• la leĝo = the law
• la posedanto = the owner
• la kaldronon = the boiler / the cauldron

Esperanto uses la much like English uses the, although Esperanto has no separate word for a/an. If there is no article, the noun can often be understood as indefinite depending on context.

The ending -anto is the active present participle used like a noun: it means a person who is doing something.

So:

• posedi = to own
• posedanto = owner, literally one who owns

This is very common in Esperanto:

• lernanto = student, learner = one who learns
• parolanto = speaker = one who speaks
• laboranto = worker = one who works

So la posedanto is literally the owning person, which is why it means the owner.

After devas (must / has to), Esperanto uses the infinitive form of the next verb.

So:

• devas ripari = must repair
• devas iri = must go
• devas pagi = must pay

This works very much like English:

• must repair
• must go
• must pay

The infinitive in Esperanto always ends in -i, so ripari is the basic dictionary form to repair.

The -n marks the direct object.

In this sentence, the owner is the one who must do the action, and the boiler is the thing being repaired. That makes la kaldronon the direct object, so it takes -n.

Compare:

• La posedanto riparas la kaldronon. = The owner repairs the boiler.
• La kaldrono funkcias. = The boiler works.

In the second example, kaldrono is the subject, so there is no -n.

Because la posedanto is the subject of the sentence, not the direct object.

In Esperanto:

• the subject usually has no special ending
• the direct object gets -n

So in: La posedanto devas ripari la kaldronon

• la posedanto = subject
• la kaldronon = direct object

That is why only kaldronon gets the accusative ending.

Esperanto word order is fairly flexible because the -n ending helps show what is the object.

The normal, neutral order here is:

• Laŭ la leĝo, la posedanto devas ripari la kaldronon.

But other orders are possible for emphasis, for example:

• La kaldronon la posedanto devas ripari.
• La posedanto laŭ la leĝo devas ripari la kaldronon.

Even so, the most natural order for learners is the ordinary one: context phrase first, then subject, then verb phrase, then object.

The comma separates an introductory phrase from the main clause.

So:

• Laŭ la leĝo, = according to the law,
• la posedanto devas ripari la kaldronon. = the owner must repair the boiler.

This comma is natural and helpful, especially when a prepositional phrase comes first. In some cases you may see Esperanto writers omit such commas, but here it is completely normal.

It can be, depending on context, but kaldrono literally means something like cauldron, boiler, or large heating vessel.

In practical modern usage, the best English translation may depend on the situation:

• in a heating or apartment context, it may be understood as boiler
• in a cooking or literal vessel context, it could be cauldron or large pot

So the Esperanto word itself is broader than one exact English word. The context usually tells you which meaning fits best.

You would make the nouns plural with -j.

For example:

• Laŭ la leĝo, la posedantoj devas ripari la kaldronojn.

That means According to the law, the owners must repair the boilers.

Notice:

• posedanto → posedantoj
• kaldronon → kaldronojn

The object still keeps -n, and the plural adds -j, so plural direct objects end in -jn.

Yes. Devi often means must, but in real usage it can also mean have to, be required to, or be supposed to, depending on context.

So this sentence could be understood as:

• the owner must repair the boiler
• the owner has to repair the boiler
• the owner is required to repair the boiler

Because the sentence begins with Laŭ la leĝo, the sense of legal obligation is especially strong here.