Mi jam preparis la portotan jakon por morgaŭ.

Esperanto does not have a separate present perfect tense like English does. The ending -is covers both ideas:

• I prepared
• I have prepared

Context tells you which English tense sounds best. Here jam makes it clear that the action is already completed, so English often uses have prepared.

Jam means already. It shows that the preparation is finished before now, or before the relevant moment.

So Mi jam preparis... gives the sense of I’ve already prepared...

Because jakon is the direct object of preparis, it takes the accusative ending -n.

Since portotan is an adjective describing jakon, it must agree with it. In Esperanto, adjectives match the noun in:

• number
• case

So:

• jako = jacket
• jakon = jacket as direct object
• portota jako = jacket to be worn
• portotan jakon = jacket to be worn, as direct object

Portotan is built from:

• port- = wear / carry
• -ot- = future passive participle
• -a = adjective ending
• -n = accusative agreement

So portota means to be worn or going to be worn.

In this sentence, la portotan jakon means something like the jacket that will be worn or the jacket to wear.

Because the jacket is not doing the wearing. The jacket is receiving that action.

• -ont- is active: the thing does the action
• -ot- is passive: the thing receives the action

So:

• portonta homo = a person who is going to wear something
• portota jako = a jacket that is going to be worn

A jacket cannot wear something, so portontan jakon would not make sense here.

La is the definite article, like English the. It shows that we are talking about a specific jacket, not just any jacket.

Esperanto has only one article:

• la = the

There is no separate word for a/an.

So la portotan jakon means a particular jacket that is understood from the situation.

Most naturally, por morgaŭ means for tomorrow in the general sense: the preparation is being done in advance of tomorrow, and the jacket is the one relevant for tomorrow.

So the phrase can feel like it applies to the whole idea, not just one single word.

If someone wanted to make the timing more explicit, they might also say:

• Mi jam preparis la jakon, kiun mi portos morgaŭ.
• Mi jam preparis la morgaŭ portotan jakon.

The original sentence is correct, but por morgaŭ is slightly broad in what it attaches to.

It is grammatical and understandable, but portotan is a fairly compact participial form. Many speakers might choose a simpler version in everyday speech, such as:

• Mi jam preparis la jakon por morgaŭ.
• Mi jam preparis la jakon, kiun mi portos morgaŭ.

The version with portotan is not wrong at all; it is just denser and a bit more formal or literary in style.

Yes. Porti can mean either wear or carry, depending on context.

For example:

• with clothes: wear
• with objects: carry

Since the noun here is jako, the meaning is clearly wear.