Соавтор уже приехал.

Соавтор means co-author.

It is built from:

• со- = co- / with
• автор = author

In this sentence, соавтор is a singular noun and refers to one co-author.

It is in the nominative case, because it is the subject of the sentence — the person who performed the action.

So the structure is basically:

Соавтор + already + arrived

Russian does not have articles like a or the.

So соавтор can mean:

• a co-author
• the co-author

Which one is meant depends on context. In many situations, English would naturally translate this as the co-author, but Russian does not need a separate word for that.

This is very common in Russian.

Russian often uses the past tense of a perfective verb where English uses the present perfect.

So уже приехал can mean:

• already arrived
• has already arrived

Russian does not need an extra word like has here. The completed meaning comes from the verb itself, especially because приехать is perfective.

In the Russian past tense, singular verbs agree with the subject in gender.

Since соавтор is masculine, the verb is приехал.

Compare:

• Соавтор уже приехал. = the co-author already arrived / has already arrived
• Соавтор уже приехала. = if the co-author is female
• Соавторы уже приехали. = if there is more than one co-author

So in the past tense:

• masculine: -л
• feminine: -ла
• neuter: -ло
• plural: -ли

Уже means already.

It shows that the action happened before now or before some expected time.

So Соавтор уже приехал suggests something like:

• the co-author is here now
• the arrival has already happened
• perhaps earlier than expected, or at least before the moment being discussed

That is the most neutral and natural position here.

Соавтор уже приехал is the standard word order.

Russian word order is flexible, but different orders change emphasis. For example:

• Соавтор уже приехал. = neutral
• Уже приехал соавтор. = more emphasis on already arrived, sometimes with a sense of surprise or announcement

So the sentence you have is the normal, unmarked version.

Приехать is a perfective verb. It describes a completed arrival.

Its imperfective partner is приезжать.

The difference is roughly:

• приехать = to arrive, to come and arrive successfully, one completed event
• приезжать = to come by vehicle repeatedly, habitually, or with focus not on the completed result

In this sentence, the speaker wants the result: the co-author has arrived and is now here. That is why приехал is used.

Originally and very often, yes.

Приехать is related to motion by transport, such as:

• car
• train
• bus
• plane

Compare:

• прийти = come on foot
• приехать = come by transport / arrive from somewhere after traveling
• прибыть = arrive, but more formal or official

In everyday Russian, though, приехать is very often just the natural verb when someone arrives from another place, especially from another city or after a trip.

Yes. Russian word order is flexible because grammatical relationships are shown less by position and more by endings and context.

Possible versions include:

• Соавтор уже приехал. = neutral
• Уже приехал соавтор. = emphasis on the fact that the co-author has already arrived
• Соавтор приехал уже. = possible in some contexts, but less neutral and often sounds contrastive

If you are unsure, Соавтор уже приехал is the safest and most natural choice.

The stress is:

соа́втор уже́ прие́хал

A rough pronunciation guide:

• соа́втор = so-AV-tor
• уже́ = oo-ZHÉ
• прие́хал = pri-YE-khal

A few notes:

• ж sounds like the s in measure
• х is the throaty sound heard in German Bach or Scottish loch
• Russian stress is important, because it is not always predictable