Bunica taie ceapa, iar eu amestec orezul în tigaie.

Because Romanian usually uses the definite form of the noun before a possessive adjective.

• bunică = grandmother / a grandmother
• bunica = the grandmother / grandma
• bunica ta = your grandmother

This is a very common Romanian pattern:

• mama mea = my mother
• fratele tău = your brother
• casa noastră = our house

So bunica ta is the normal way to say your grandmother.

In Romanian, possessive adjectives usually come after the noun, not before it as in English.

So:

• bunica ta = your grandmother
• literally: grandmother-the your

This is standard Romanian word order. English says your grandmother, but Romanian prefers grandmother your.

Also, ta is used because bunica is feminine singular. Compare:

• bunicul tău = your grandfather
• bunica ta = your grandmother

Those endings are the definite article attached to the noun.

Romanian usually puts the at the end of the noun:

• ceapă = onion

• ceapa = the onion

• orez = rice
• orezul = the rice

So in this sentence, the speaker is talking about specific onion and rice, not just any onion or rice.

This attached definite article is one of the most important features of Romanian grammar.

Taie is the 3rd person singular present form of a tăia = to cut.

Here the subject is bunica = grandma / your grandmother, which is she, so you need the he/she form:

• eu tai = I cut
• tu tai = you cut
• el/ea taie = he/she cuts

So:

• Bunica taie ceapa = Grandma cuts the onion

Even though the infinitive has ă (a tăia), the present form here is taie.

Yes, Romanian often leaves out subject pronouns because the verb ending usually already shows the subject.

So amestec by itself already means I stir / I mix.

But in this sentence, eu is included for emphasis or contrast:

• Bunica taie ceapa, iar eu amestec orezul...
• Grandma cuts the onion, and I stir the rice...

The sentence is contrasting two people doing two different actions, so eu sounds natural and helpful.

Iar often means something like:

• and
• while
• whereas
• and as for

It often introduces a contrast or parallel action.

So here:

• Bunica taie ceapa, iar eu amestec orezul în tigaie.

gives the sense of:

• Grandma is cutting the onion, while I am stirring the rice in the pan.

If you used și, it would simply mean and, with less contrast. Iar is a good choice when switching attention from one subject to another.

Amestec is the 1st person singular present form of a amesteca = to stir / to mix.

Because the subject is eu = I, you need the I form:

• eu amestec = I stir / I mix
• tu amesteci = you stir
• el/ea amestecă = he/she stirs

So:

• eu amestec orezul = I stir the rice

This is just the normal present-tense form for eu.

Both can exist, but they do not feel exactly the same.

• în tigaie = in a pan / in the pan, with a more general, activity-focused feel
• în tigaia = in the pan, referring to a more specific, clearly identified pan

In everyday Romanian, în tigaie is very natural in cooking contexts. It often focuses more on where the action is happening than on identifying one particular pan.

So amestec orezul în tigaie sounds like a normal cooking sentence.

Yes. Romanian often uses the definite article where English might simply use a bare noun.

• orez = rice
• orezul = the rice

In context, orezul usually means the rice that is already being prepared or talked about. Since this is a cooking situation, Romanian naturally treats it as a specific thing.

English and Romanian do not always match exactly in article usage, so this is something learners get used to over time.

The basic word order is Subject – Verb – Object:

• Bunica | taie | ceapa
• eu | amestec | orezul

Then în tigaie adds place/location:

• eu amestec orezul în tigaie

This word order is very normal and natural in Romanian.

Romanian is somewhat flexible, but this sentence uses a straightforward, standard structure.

În means in or inside.

So:

• în tigaie = in the pan

It is a very common preposition in Romanian. In this sentence, it shows the place where the stirring happens.

Also, note the spelling: în uses the Romanian letter î.

A rough English-style guide would be:

• Bunica ≈ boo-NEE-ka
• taie ≈ TAH-yeh
• ceapa ≈ CHAH-pa
• iar ≈ yar
• eu ≈ eh-oo (said quickly, almost like one syllable)
• amestec ≈ a-MES-tek
• orezul ≈ o-REH-zool
• în ≈ a short nasal-ish u/i sound that has no exact English match
• tigaie ≈ tee-GAH-yeh

Putting it together:

boo-NEE-ka TAH-yeh CHAH-pa, yar eh-oo a-MES-tek o-REH-zool uhn tee-GAH-yeh

That is only an approximation, but it can help you get started.