Mi akceptis vian inviton al la festo.

In Esperanto, the verb ending -is marks the past tense.

So:

• akcepti = to accept
• akceptas = accept / am accepting
• akceptis = accepted
• akceptos = will accept

So Mi akceptis means I accepted.

The ending -n marks the direct object in Esperanto.

Here, the thing being accepted is your invitation, so inviton gets -n.

Because vian describes inviton, it must match it in grammar. In Esperanto, adjectives and possessive-type words agree with the noun they modify in both number and case.

So:

• via invito = your invitation
• vian inviton = your invitation, as a direct object

That is why both words have -n.

Because via is modifying a noun that is in the accusative.

The noun is inviton, and since it has -n, the related word must also take -n:

• via invito = your invitation
• vian inviton = your invitation as the object of the verb

This agreement rule is very regular in Esperanto.

al usually means to.

So al la festo literally means to the party.

In this sentence, it goes with inviton:

• invito al la festo = invitation to the party

So the structure is:

• Mi akceptis = I accepted
• vian inviton = your invitation
• al la festo = to the party

It does not mean that I accepted toward the party. It describes what kind of invitation it was.

la is the definite article, meaning the.

Esperanto has only one article: la. There is no separate word for a or an.

So:

• festo = party / a party
• la festo = the party

In this sentence, la festo refers to a specific party that both speaker and listener can identify.

Because Esperanto has no indefinite article.

English distinguishes between:

• an invitation
• the invitation

Esperanto only marks the definite article:

• invito = invitation / an invitation
• la invito = the invitation

So vian inviton already means your invitation without needing any extra word like an.

It is connected to inviton.

The idea is:

• your invitation to the party

not:

• accepted to the party

So the phrase groups like this:

Mi akceptis [vian inviton al la festo].

That is an important reading point for learners, because English also uses to, but here it belongs to invitation.

The dictionary forms are:

• mi = I
• akcepti = to accept
• via = your
• invito = invitation
• al = to
• la = the
• festo = party

In the sentence, some of them change form because of grammar:

• akcepti → akceptis for past tense
• via → vian to agree with the accusative object
• invito → inviton because it is the direct object

Yes, Esperanto word order is fairly flexible because endings show the grammar.

The normal order here is:

Mi akceptis vian inviton al la festo.

But other orders are possible, especially for emphasis, such as:

• Vian inviton al la festo mi akceptis.

This still means the same thing, because -n shows that vian inviton is the object.

That said, the original order is the most neutral and natural for most learners to use.

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

So:

• Mi = one syllable
• akceptis = ak-CEP-tis
• vian = VI-an
• inviton = in-VI-ton
• festo = FES-to

A rough pronunciation guide is:

mee ak-TSEP-tees VEE-an een-VEE-ton al la FES-to

The spelling is very regular, so pronunciation becomes predictable once you learn the sound system.