To explain why something happened, Russian makes you choose which half of the cause-and-effect pair you're pointing at. Потому́ что introduces the cause ("because X"); поэ́тому introduces the result ("therefore Y"). They're two ends of the same arrow, and the most common error English speakers make is using one where they need the other. Add е́сли ("if"), with its surprising future tense, and так как / поско́льку for fronted, more formal causes, and you have the everyday toolkit for explaining and supposing.
потому́ что — the cause: "because"
Потому́ что answers the question почему́? ("why?"). It introduces the reason, and it normally comes after the result clause — it can't easily start a sentence. A comma always precedes the whole conjunction.
Я не пришёл, потому́ что был бо́лен.
I didn't come because I was ill. (the result first, then потому́ что + the cause)
Она́ улыба́ется, потому́ что получи́ла хоро́шие но́вости.
She's smiling because she got good news. (the reason behind the smiling)
There's an optional, slightly emphatic variant where the потому́ stays with the main clause and only что introduces the subordinate clause, with the comma moving inside: Я не пришёл потому́, что был бо́лен ("The reason I didn't come is that I was ill"). This shifts focus onto the cause and is common in careful or written style. The neutral, everyday version keeps потому́ что together.
поэ́тому — the result: "therefore / so"
Поэ́тому is the mirror image: it introduces the result / consequence, "and that's why / therefore / so." The cause comes first, then поэ́тому + the result. It is not a subordinating conjunction joining a dependent clause — it's a connector between two main clauses, and a comma precedes it.
Я был бо́лен, поэ́тому не пришёл.
I was ill, so I didn't come. (cause first, then поэ́тому + result)
По́езд опа́здывал, поэ́тому мы пое́хали на такси́.
The train was late, so we took a taxi. (late train = cause; taxi = result)
так как / поско́льку — "since / because", and they can front the sentence
A key limitation of потому́ что: it can't naturally begin a sentence. When you want the cause to come first — "Since it was raining, we stayed home" — Russian reaches for так как or the more formal поско́льку. Both mean "since / because / inasmuch as," and both can stand at the front, with a comma closing the clause before the main one.
Так как шёл дождь, мы оста́лись до́ма.
Since it was raining, we stayed home. (cause fronted — потому́ что couldn't do this)
Поско́льку бюдже́т ограни́чен, прое́кт отложи́ли.
Since the budget is limited, the project was postponed. (поско́льку — more formal/written register)
So all three relate cause to effect, but they're not stylistically equal: потому́ что is the neutral everyday "because" (clause-final); так как is "since" and can front; поско́льку is the same but (formal), at home in writing and official speech.
из-за того́ что and благодаря́ тому́ что — flavoured causes
Russian can also colour the cause as negative or positive. Из-за того́ что = "because of (the fact that)," carrying a negative or unwelcome flavour (the cause is something bad). Благодаря́ тому́ что = "thanks to (the fact that)," for a welcome cause.
Из-за того́ что отмени́ли рейс, мы опозда́ли на сва́дьбу.
Because the flight was cancelled, we were late for the wedding. (negative cause → из-за того́ что)
Благодаря́ тому́ что ты помо́г, мы всё успе́ли.
Thanks to your help, we got everything done in time. (positive cause → благодаря́ тому́ что)
е́сли — "if": real conditions, with a future twist
Е́сли introduces a real, open condition ("if X, then Y"). The single fact English speakers must absorb: when the condition is in the future, Russian puts the verb in the future tense in both clauses — where English uses the present in the if-clause.
Е́сли бу́дет вре́мя, я приду́.
If I have time, I'll come. (Russian: 'if there WILL BE time' — бу́дет is future, where English says 'have')
Е́сли ты позвони́шь, я отве́чу.
If you call, I'll answer. (позвони́шь is future-perfective — English 'call' is present in form, future in meaning)
English hides the futurity of the if-clause behind a present-tense form; Russian makes it explicit. There is no rule that the verb in the е́сли-clause must match English's present tense — match the meaning, which is future, and use the future. This is the same logic that governs когда́ ("when") and is detailed on The future in subordinate clauses.
The optional то ("then") can introduce the main clause for clarity, especially when the е́сли-clause is long: Е́сли бу́дет вре́мя, то я приду́. A comma always separates the two clauses, with or without то.
Comma placement at a glance
| Conjunction | Means | Position | Comma |
|---|---|---|---|
| потому́ что | because (cause) | clause-final (can't front) | before потому́ что |
| поэ́тому | therefore / so (result) | after the cause clause | before поэ́тому |
| так как | since / because | can front the sentence | before the main clause |
| поско́льку (formal) | since / because | can front the sentence | before the main clause |
| е́сли | if (real condition) | usually fronts | before the main clause / то |
Common Mistakes
❌ Я был бо́лен, потому́ что не пришёл.
Cause/result swapped — this says 'I was ill because I didn't come.' The illness is the cause, so the result needs поэ́тому.
✅ Я был бо́лен, поэ́тому не пришёл.
I was ill, so I didn't come. (cause → поэ́тому → result)
❌ Потому́ что шёл дождь, мы оста́лись до́ма.
Wrong — потому́ что can't start the sentence. To front the cause, use так как (or поско́льку).
✅ Так как шёл дождь, мы оста́лись до́ма.
Since it was raining, we stayed home.
❌ Е́сли у меня́ есть вре́мя, я приду́.
Tense mismatch — the condition is in the future, so Russian needs the future (бу́дет вре́мя), not the present есть, even though English uses the present 'have'.
✅ Е́сли бу́дет вре́мя, я приду́.
If I have time, I'll come.
❌ Она́ ра́да поэ́тому сдала́ экза́мен.
Wrong conjunction — 'she's happy BECAUSE she passed' points to the cause, so it needs потому́ что, not the result-word поэ́тому.
✅ Она́ ра́да, потому́ что сдала́ экза́мен.
She's happy because she passed the exam.
Key Takeaways
- Потому́ что = the cause ("because"), answers почему́?, sits clause-final and can't start a sentence. Поэ́тому = the result ("therefore / so"). Same two facts in opposite order take opposite conjunctions — never swap them.
- To put the cause first, use так как ("since") or the formal поско́льку — both can front the sentence where потому́ что cannot.
- Flavoured causes: из-за того́ что (because of — negative) vs благодаря́ тому́ что (thanks to — positive).
- Е́сли ("if") introduces real conditions and takes the future tense when the condition is future — where English uses the present (Е́сли бу́дет вре́мя, я приду́). Optional то can open the main clause.
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- Subordinating: Что and ЧтобыA2 — Что and чтобы look alike but do opposite jobs. Что (that) reports a fact after verbs of speaking, thinking, and knowing — and, unlike English 'that', it can never be dropped. Чтобы (in order to / that) introduces a goal or a wish, taking an infinitive when the subject stays the same and the past tense when it changes. This page draws the factual/volitional line and nails the obligatory comma.
- Temporal Conjunctions: когда, пока, после того как, как толькоB1 — Conjunctions of time tell you when one event happens relative to another: когда́ (when), пока́ (while) and пока́…не (until), как то́лько (as soon as), and the compound after/before pairs по́сле того́ как, пе́ред тем как, до того́ как, с тех пор как. The headline rule for English speakers: когда́- and пока́-clauses about the future take the FUTURE tense, where English uses the present.
- Future Tense in Subordinate ClausesB1 — English says 'when I arrive [present], I'll call'. Russian puts BOTH clauses in the future: Когда́ я прие́ду, я тебе́ позвоню́. After когда́, е́сли, как то́лько, пока́ referring to a future event, the subordinate verb must be future — writing a present there (*Когда́ я приезжа́ю…*) is one of the most systematic English-transfer errors.