Mi estas laca, sed mi tamen iros al la biblioteko.

Iros comes from the verb iri, meaning to go.

The ending -os marks the future tense, so:

• iras = go / am going
• iris = went
• iros = will go

So mi iros means I will go.

A useful thing to remember is that Esperanto verbs do not change for person:

• mi iros = I will go
• vi iros = you will go
• li iros = he will go

Only the tense ending changes.

Because laca is a predicate adjective after estas, not a direct object.

In Esperanto, adjectives normally end in -a. The -n ending is used for:

• direct objects
• direction in some cases

Here, laca describes mi after the verb estas:

• Mi estas laca = I am tired

That is different from something like:

• Mi vidas lacan studenton = I see a tired student

There, lacan gets -n because it agrees with studenton, which is a direct object.

Because Esperanto normally uses esti + adjective to describe a state, just like English uses to be + adjective.

So:

• Mi estas laca = I am tired

This is the normal way to express a condition.

You would not normally replace it with Mi lacas. In standard Esperanto, laci means to tire someone, while laciĝi means to get tired.

So compare:

• Mi estas laca = I am tired
• Mi laciĝas = I am getting tired

Not really. They do related but different jobs.

• sed = but
• tamen = nevertheless / still / all the same

So the sentence means something like:

• I am tired, but I will nevertheless go to the library.

Using both makes the contrast stronger. It sounds natural in Esperanto.

If you remove tamen, the sentence is still correct:

• Mi estas laca, sed mi iros al la biblioteko.

That just sounds a little less emphatic.

Because Esperanto often repeats the subject in a new clause, especially after a conjunction like sed.

So:

• Mi estas laca, sed mi tamen iros...

is very natural.

Repeating mi is especially helpful because Esperanto verb forms show tense, but they do not show person. For example, iros could mean I will go, you will go, they will go, and so on, depending on context.

That means repeating the subject often keeps the sentence clearer than in English.

Because al shows movement toward a place:

• al la biblioteko = to the library

By contrast, en shows location inside a place:

• en la biblioteko = in the library

So:

• Mi iros al la biblioteko = I will go to the library
• Mi estas en la biblioteko = I am in the library

If you specifically want to emphasize going into the inside of the library, Esperanto can also use en with the accusative:

• Mi iros en la bibliotekon = I will go into the library

But al la biblioteko is very common and natural for go to the library.

La is the definite article, like English the.

So la biblioteko means the library, usually a specific one that is known from the situation or context.

Without la, biblioteko would be more indefinite, like a library or simply library in a more general sense.

So the sentence suggests a particular library, not just any library.

Yes. Esperanto word order is fairly flexible, and tamen can move around depending on emphasis.

For example, these are all possible:

• Mi estas laca, sed mi tamen iros al la biblioteko.
• Mi estas laca, sed tamen mi iros al la biblioteko.
• Mi estas laca, sed mi iros tamen al la biblioteko.

The version in your sentence is very natural. Placing tamen before iros gives it scope over the action: I will nevertheless go.

Moving it changes the emphasis a little, but not the basic meaning.

Yes, it is normal and expected.

In Esperanto, a comma is usually used before coordinating conjunctions like sed when they connect two clauses:

• Mi estas laca, sed mi tamen iros al la biblioteko.

This is similar to English punctuation in many cases.

Esperanto pronunciation is very regular. The stress is almost always on the second-to-last syllable of each word.

So this sentence is stressed like this:

• MI ES-tas LA-tsa, sed mi ta-MEN I-ros al la bi-bli-o-TE-ko.

A few pronunciation notes:

• c is pronounced ts, so laca sounds like LA-tsa
• r is usually tapped or lightly rolled
• e is always a clear eh sound, not a silent letter
• o is a clear oh sound

Because Esperanto spelling is very consistent, once you know the sounds, you can usually pronounce a word correctly just by reading it.

Yes.

You can say:

• Mi estas laca, sed mi iros al la biblioteko.

That is completely grammatical and natural.

Adding tamen gives a stronger sense of:

• even so
• still
• nevertheless
• all the same

So the choice is about nuance, not correctness.