Mia patro kuiras viandon kun cepoj, dum mia patrino preparas terpomojn.

Because mia is a possessive adjective, and adjectives in Esperanto end in -a.

• mia = my
• patro = father

So mia patro means my father.

Mio is not used this way. A native English speaker may expect something like my versus mine, and Esperanto does make a similar distinction:

• mia patro = my father
• la patro estas mia = the father is mine

So before a noun, you use mia, not mio.

Esperanto often builds related words very regularly.

• patro = father
• patrino = mother

The key part is the suffix -in-, which marks the female form.

So:

• patro = father
• patrino = mother
• frato = brother
• fratino = sister

This is a very common pattern in Esperanto vocabulary.

The -n ending marks the direct object in Esperanto.

In this sentence:

• Mia patro kuiras viandon
• My father cooks meat

The thing being cooked is meat, so viando becomes viandon.

This is called the accusative ending.

A useful way to think about it:

• the subject does the action
• the direct object receives the action

Here:

• mia patro = subject
• kuiras = verb
• viandon = direct object

Because terpomojn is a plural direct object, while cepoj is just plural after a preposition.

Breakdown:

• terpomo = potato
• terpomoj = potatoes
• terpomojn = potatoes as a direct object

In mia patrino preparas terpomojn, the potatoes are what the mother prepares, so they take -n.

But in kun cepoj:

• kun = with
• cepoj = onions

After a preposition like kun, you normally do not add -n just because it is an object in English. So kun cepoj is correct, not kun cepojn.

So:

• -j = plural
• -n = direct object
• -jn = plural direct object

Dum means while or during the time that.

In this sentence, it connects two actions happening at the same time:

• Mia patro kuiras viandon kun cepoj
• dum
• mia patrino preparas terpomojn

So the idea is:

• My father is cooking meat with onions, while my mother is preparing potatoes.

It shows simultaneous actions.

Because possessives like mia, via, lia, ŝia, and so on already make the noun specific.

So:

• mia patro already means my father
• mia patrino already means my mother

Adding la would usually be unnecessary.

This is similar to English: we say my father, not the my father.

So in Esperanto, mia patro is the normal form.

They are related, but not identical.

• kuiri = to cook
• prepari = to prepare

So:

• kuiras viandon = is cooking meat
• preparas terpomojn = is preparing potatoes

Prepari is a bit broader. It can mean getting something ready, not necessarily cooking it fully. For example, someone could be washing, peeling, or cutting the potatoes.

That is why the sentence can naturally use two different verbs.

Because viando is often treated like a mass noun, similar to meat in English.

In English, we usually say:

• I am cooking meat not
• I am cooking meats

Likewise in Esperanto:

• viando = meat, in a general mass sense

But potatoes and onions are usually thought of as countable items:

• terpomoj = potatoes
• cepoj = onions

So this difference is natural and matches English quite closely.

The ending -as marks the present tense in Esperanto.

So:

• kuiras = cooks / is cooking
• preparas = prepares / is preparing

Esperanto does not usually force a distinction between simple present and present progressive the way English sometimes does. Context tells you which is more natural.

So kuiras can mean:

• cooks
• is cooking

and preparas can mean:

• prepares
• is preparing

Yes, Esperanto word order is fairly flexible, mainly because the -n ending shows the direct object.

The normal order here is:

• Mia patro kuiras viandon kun cepoj

But you could also say:

• Viandon kun cepoj kuiras mia patro

This is still understandable because viandon has -n, so you know it is the object.

That said, the original word order is the most neutral and easiest for learners:

• subject + verb + object

So it is the best version to imitate at first.

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

So:

• MI-a
• PA-tro
• ku-I-ras
• vi-AN-don
• kun
• ce-POJ
• dum
• pa-TRI-no
• pre-PA-ras
• ter-PO-mojn

This rule is very regular, which is one of the helpful things about Esperanto pronunciation.