Ben bugün kahve içmiyorum, onun yerine çay içiyorum.

That’s true: Turkish often leaves out subject pronouns because the verb ending already shows the subject.

• içiyorum = I am drinking
• içmiyorum = I am not drinking

So Ben is not required here. The sentence could also be:

• Bugün kahve içmiyorum, onun yerine çay içiyorum.

Including Ben can add a little emphasis or clarity, especially if the speaker is contrasting themselves with someone else.

Bugün means today, and it sets the time frame for the whole sentence.

Putting it near the beginning is very natural in Turkish because it tells the listener right away when this is true:

• Ben bugün kahve içmiyorum...

But Turkish word order is fairly flexible, so you can move bugün for different emphasis:

• Bugün kahve içmiyorum.
• Kahve içmiyorum bugün.

All of these are possible, though the version in your sentence is very natural and neutral.

Yes. These forms use the -iyor pattern, which is commonly called the present continuous.

• içiyorum = I am drinking
• içmiyorum = I am not drinking

But in Turkish, this form is used a bit more widely than English am drinking. It can describe:

• something happening right now
• a current temporary situation
• a present choice or routine

So in this sentence, it means something like: Today, I’m not drinking coffee; I’m drinking tea instead. It does not have to mean the speaker is literally sipping tea at this exact second.

A helpful beginner breakdown is:

• iç- = drink
• -m- = negative
• -iyor = present continuous
• -um = I

So:

• içiyorum = I am drinking
• içmiyorum = I am not drinking

You do not need to memorize every sound change right away; the important pattern is:

• geliyorum / gelmiyorum
• yapıyorum / yapmıyorum
• içiyorum / içmiyorum

This is a very common verb pattern in Turkish.

Because the present continuous suffix changes according to vowel harmony. Its basic pattern is:

• -ıyor
• -iyor
• -uyor
• -üyor

The choice depends on the last vowel of the verb stem.

Since iç- contains i, the correct form is:

• içiyorum
• içmiyorum

You’ll see the same pattern in other verbs:

• bakıyorum
• gidiyorum
• oturuyorum
• gülüyorum

Because they are being used as general, non-specific objects.

• kahve içiyorum = I drink / am drinking coffee in a general sense
• çay içiyorum = I drink / am drinking tea in a general sense

In Turkish, the accusative is usually used when the object is specific or definite.

Compare:

• Kahve içiyorum. = I’m drinking coffee.
• Kahveyi içiyorum. = I’m drinking the coffee / that specific coffee.

So in your sentence, no accusative is needed because the speaker is talking about coffee and tea in general as drink choices.

Onun yerine is a very common expression meaning:

• instead of that
• in its place
• instead

In this sentence, onun refers back to kahve.

So the idea is:

• Ben bugün kahve içmiyorum, onun yerine çay içiyorum.
• I’m not drinking coffee today; instead, I’m drinking tea.

It is a natural way to avoid repeating kahve again.

Because yerine normally combines with the genitive form of pronouns.

So:

• benim için = for me
• onun gibi = like him/her/it
• onun yerine = instead of him/her/it

Here, onun is the genitive form of o.

Also, Turkish uses o / onun not only for people, but also for things. So onun can refer to kahve just fine.

Yes, absolutely.

Both are natural:

• Ben bugün kahve içmiyorum, onun yerine çay içiyorum.
• Ben bugün kahve yerine çay içiyorum.

The difference is mostly stylistic:

• onun yerine avoids repeating kahve
• kahve yerine is more direct

Both mean essentially the same thing here.

In a full, standard sentence, yes, repeating the verb is normal and natural:

• ... onun yerine çay içiyorum.

Turkish often keeps the verb in each clause rather than leaving it out the way English sometimes can.

In very casual speech, people may shorten things if the meaning is obvious, but for learners, it’s best to use the full version with the verb repeated.

Not completely. Turkish word order is flexible, but the verb usually comes near the end of the clause.

Your sentence has a very natural order:

• Ben bugün kahve içmiyorum, onun yerine çay içiyorum.

You can move some parts around for emphasis, for example:

• Bugün kahve içmiyorum, onun yerine çay içiyorum.
• Ben kahve içmiyorum bugün, onun yerine çay içiyorum.

But the version you have is a good, standard model to learn from. It sounds natural and clear.