La skatolo estas tro peza por mi.

In Esperanto, all nouns end in -o. So skatolo is clearly a noun.

This is one of the most useful regular patterns in Esperanto:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb

So when you see skatolo, you can immediately recognize it as a noun.

Because peza is an adjective, and Esperanto adjectives always end in -a.

Here, peza describes skatolo, so it means that the box has the quality of being heavy.

A key point: adjectives in Esperanto agree with the noun they describe in number and case. In this sentence, skatolo is singular and not accusative, so peza stays in its basic form:

• skatolo → singular noun
• peza → singular adjective matching it

If the noun were plural, the adjective would also become plural:

• La skatoloj estas tro pezaj por mi.

Tro means too in the sense of excessively.

It modifies the adjective peza, so:

• peza = heavy
• tro peza = too heavy

This works very much like English too heavy.

Since tro is an adverb, it modifies adjectives, adverbs, or verbs:

• tro peza = too heavy
• tro rapide = too quickly
• tro laboras = works too much

Estas is the present-tense form of esti, meaning to be.

So:

• esti = to be
• estas = is / am / are

One nice thing about Esperanto is that the verb form does not change depending on the subject:

• mi estas = I am
• vi estas = you are
• li estas = he is
• la skatolo estas = the box is

So estas is used here simply because the sentence says what the box is: too heavy for me.

Here, por mi means for me in the sense of for me to handle, use, carry, lift, etc.

That is the normal pattern in Esperanto with this kind of idea:

• tro + adjective + por + person

So:

• tro peza por mi = too heavy for me

Using al mi would suggest something more like to me, which is not the idea here.

Compare:

• Tio estas grava por mi. = That is important for me.
• Donu tion al mi. = Give that to me.

So in your sentence, por mi is the correct choice because it expresses suitability or ability in relation to me.

Because Esperanto can leave that action understood if the meaning is clear from context.

So La skatolo estas tro peza por mi can naturally mean something like:

• too heavy for me to carry
• too heavy for me to lift
• too heavy for me to move

If you want to be more explicit, you can add the infinitive:

• La skatolo estas tro peza por mi levi. = The box is too heavy for me to lift.
• La skatolo estas tro peza por mi porti. = The box is too heavy for me to carry.

Without that extra verb, the sentence is still perfectly natural if the omitted action is obvious.

La is the definite article, equivalent to English the.

So la skatolo means the box.

Unlike English articles, la does not change:

• no separate form for plural
• no separate form for gender
• no separate form for case

It is always just la.

Actually, in this sentence peza is not directly attached to the noun in the same way as in la peza skatolo.

Here the structure is:

• La skatolo = subject
• estas = linking verb
• tro peza = predicate adjective

So this is like English:

• The box is heavy

not like:

• the heavy box

If you wanted to say the heavy box, you would put the adjective before the noun:

• la peza skatolo

But after estas, it is normal for the adjective to come in the predicate:

• La skatolo estas peza.

Yes, Esperanto word order is fairly flexible, but this sentence uses the most neutral and natural order:

• La skatolo = subject
• estas = verb
• tro peza por mi = complement

That said, Esperanto can move things around for emphasis. For example:

• Tro peza por mi estas la skatolo.

This is understandable, but it sounds more marked or literary. For ordinary speech and writing, La skatolo estas tro peza por mi is the best choice.

In Esperanto, mi is used for both I and me. It does not change form the way English pronouns do.

So:

• Mi vidas la skatolon. = I see the box.
• La skatolo estas tro peza por mi. = The box is too heavy for me.

Esperanto generally avoids separate subject/object forms for most personal pronouns. Instead, relationships are shown by word order, prepositions, and the accusative -n where needed.

Here, por already shows the role of mi, so no other change is needed.

In Esperanto, the stress is almost always on the second-to-last syllable.

So:

• la ska-TO-lo
• ES-tas
• tro PE-za
• por MI

That makes pronunciation very regular.

For the whole sentence, a rough pronunciation guide is:

• la ska-TO-lo ES-tas tro PE-za por MI

Yes. This is a good way to see how Esperanto endings work.

If the boxes were plural:

• La skatoloj estas tro pezaj por mi.
  • skatolo → skatoloj
  • peza → pezaj

The adjective changes too, because adjectives agree with nouns.

If the box were the direct object of a verb, the noun would take -n:

• Mi movas la skatolon. = I move the box.

And if an adjective directly described that accusative noun, the adjective would also take -n:

• Mi movas la pezan skatolon.

So the sentence you were given is in the simplest singular, non-accusative form.