Врач определил причину приступа.

Because причину is the direct object of the verb определил (determined / identified), so it is in the accusative case.

The noun is:

• причина = cause, reason

Its forms are:

• nominative: причина
• accusative: причину

So:

• Врач определил причину приступа.
• literally: The doctor determined the cause of the attack/seizure.

Because приступа is in the genitive singular.

Here, Russian uses the genitive to express of the attack / of the seizure:

• причина приступа = the cause of the attack

This is a very common pattern in Russian:

• причина болезни = the cause of the illness
• начало урока = the beginning of the lesson
• конец фильма = the end of the film

So приступа depends on причину and tells us the cause of what?

In this sentence, определил usually means determined, identified, or established, not defined in the dictionary sense.

So:

• Врач определил причину приступа = The doctor determined/identified the cause of the attack.

The verb is:

• определить = perfective
• определять = imperfective

In medical or analytical contexts, определить often means figure out, diagnose, or establish.

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

Here:

• определил = masculine singular past tense

That matches врач, which is grammatically treated as masculine here.

Compare:

• врач определил = the doctor determined (male doctor, or doctor treated grammatically as masculine)
• врач определила = the doctor determined (female doctor)

So if you know the doctor is a woman, Russian often uses:

• Врач определила причину приступа.

Even though the noun врач itself usually stays the same.

Because врач is one of those Russian nouns that is traditionally masculine in form but can refer to either a man or a woman.

So:

• врач = doctor
• the noun stays врач
• the verb often shows the person’s gender in the past tense

Examples:

• Этот врач очень опытный. = This doctor is very experienced.
• Эта врач очень опытная. = This doctor is very experienced.
• Врач пришёл. = The doctor came. (male)
• Врач пришла. = The doctor came. (female)

So gender is often shown by adjectives, pronouns, or past-tense verbs.

Russian has no articles.

So Russian does not normally use separate words for:

• a
• an
• the

That means врач can mean:

• a doctor
• the doctor

and причину can mean:

• a cause
• the cause

You figure it out from the context.

So this sentence could be understood as:

• The doctor determined the cause of the attack or
• A doctor determined the cause of an attack

In real context, it will usually be clear which is meant.

The word order here is the most neutral one:

• Врач = subject
• определил = verb
• причину приступа = object

So it is basically:

• Subject + Verb + Object

Yes, Russian word order can be changed, but the emphasis changes.

For example:

• Врач определил причину приступа.
  Neutral: The doctor determined the cause of the attack.

• Причину приступа определил врач.
  Emphasis on it was the doctor who determined it.

• Определил врач причину приступа.
  Less neutral, more stylistically marked.

Because Russian uses cases, word endings help show the grammatical roles even when the order changes.

Here are the dictionary forms:

• врач = doctor
• определить = to determine, identify
• причина = cause, reason
• приступ = attack, seizure, fit, bout

And here are the forms actually used in the sentence:

• врач = nominative singular
• определил = past tense, masculine singular
• причину = accusative singular
• приступа = genitive singular

Приступ often means a sudden episode or attack, especially in medical contexts.

Depending on context, it can mean:

• attack
• seizure
• fit
• bout

Examples:

• приступ кашля = a coughing fit
• приступ астмы = an asthma attack
• сердечный приступ = heart attack

So in причина приступа, the exact English translation depends on the medical situation.

Because Russian often expresses of relationships with the genitive case, not with a separate preposition.

In English, you say:

• the cause of the attack

In Russian, you say:

• причина приступа

No extra word is needed. The ending -а on приступа shows that relationship.

This is very common in Russian:

• дверь комнаты = the door of the room
• центр города = the center of the city
• цвет машины = the color of the car

The stress is:

• врач
• определи́л
• причи́ну
• при́ступа

So roughly:

• Врач определи́л причи́ну при́ступа.

A very rough English-style pronunciation guide would be:

• vrach ahp-ree-dee-LYEEL pree-CHEE-noo PREE-stoo-puh

A few notes:

• врач has a short, compact sound, almost like vrach
• ч is like ch in church
• unstressed о is often pronounced closer to a in normal speech

Because определил comes from определить, the perfective verb, which presents the action as completed.

So the sentence implies that the doctor successfully arrived at a result:

• the cause was determined

If you used the imperfective определял, it would suggest process, repetition, or an ongoing attempt, depending on context.

Compare:

• Врач определил причину приступа.
  The doctor determined the cause of the attack.
  Completed result.

• Врач определял причину приступа.
  The doctor was determining / tried to determine the cause of the attack.
  Focus on the process, not necessarily the completed result.