Compound and Complex Sentences | Ukrainian Grammar

A single clause — one subject, one predicate — is a simple sentence: Я чита́ю "I'm reading." But real speech strings clauses together, and Ukrainian does it in two structurally different ways. When the clauses are equal partners, joined by and / but / or, you get a compound sentence. When one clause is the boss and the other hangs off it as a that / when / because / if clause, you get a complex sentence. The two patterns punctuate differently and use different connecting words, and Ukrainian is far stricter about commas than English: the comma before a subordinate clause is obligatory, and the linking word is never dropped. This page sorts the three sentence types and nails down where the comma goes.

Simple → compound → complex

Start with the ladder:

Simple (про́сте) — one clause: Я чита́ю. "I'm reading."
Compound (складносуря́дне) — two or more independent clauses of equal rank, joined by a coordinating conjunction (і, а, але́, або́, та): Я чита́ю, а він спить. "I'm reading, and he's sleeping." Either clause could stand alone.
Complex (складнопідря́дне) — a main clause plus a subordinate clause that depends on it, joined by a subordinating word (що, щоб, коли́, бо, якщо́, який): Я зна́ю, що ти прийде́ш. "I know that you'll come." The subordinate clause cannot stand alone — "*that you'll come" is a fragment.

The difference is rank. In a compound sentence the clauses are siblings; in a complex sentence one clause is embedded inside, or attached under, the other.

Compound sentences: equal clauses, coordinating conjunctions

A compound sentence links clauses that could each be a sentence on their own. The everyday coordinators are:

Conjunction	Meaning	Relation
і / й	and	addition (й after a vowel)
та	and / but	addition (slightly bookish)
а	and / whereas / but	contrast, juxtaposition
але́	but	adversative, opposition
або́	or	alternative

The pair to watch is а vs але́. а marks a soft contrast or "whereas" — two facts set side by side (Я чита́ю, а він спить "I read, whereas he sleeps"). але́ marks a sharp "but" — a real obstacle or reversal (Хочу́, але́ не мо́жу "I want to, but I can't"). English "but" covers both; Ukrainian splits them. (Full detail on the coordinating conjunctions page.)

Я чита́в, а він спав — ти́ха була́ ні́чка.

I was reading, and he was sleeping — it was a quiet little night. — а, soft contrast between two equal clauses.

Хо́чу піти́ з ва́ми, але́ за́втра ра́но встава́ти.

I want to go with you, but I have to get up early tomorrow. — але́, a real 'but' / obstacle.

Поспіши́, або́ ми запізни́мося на по́тяг.

Hurry up, or we'll miss the train. — або́, alternative; comma before it as the clauses are independent.

Note the comma: in standard compound sentences a comma stands before а, але́, або́ (and usually before contrastive і). The clauses are independent, so the comma fences them.

Complex sentences: a main clause + a subordinate clause

In a complex sentence one clause is subordinate — it answers a question the main clause raises (what? when? why? on what condition? which?) and is introduced by a subordinating conjunction or a relativizer:

Subordinator	Meaning	Clause type
що	that	complement (after say/think/know)
щоб	so that / in order to	purpose
коли́	when	time
бо / тому́ що	because	cause
якщо́	if	condition
яки́й	which / who / that	relative (modifies a noun)

Я зна́ю, що ти прийде́ш — ти ні́коли не підво́див.

I know (that) you'll come — you've never let me down. — complex sentence with the complement що; the comma is obligatory.

Він зателефонува́в, коли́ стемні́ло.

He called when it got dark. — time clause with коли́; comma before the subordinator.

Я не пішо́в на робо́ту, бо захворі́в.

I didn't go to work because I fell ill. — cause clause with бо; comma before it.

Зателефону́й мені́, якщо́ щось зміни́ться.

Call me if anything changes. — condition clause with якщо́.

A relative clause (introduced by який or що) is also a subordinate clause — it modifies a noun rather than answering when/why — and it follows the same comma rule. The mechanics of який agreeing with its antecedent are on the relative clauses page.

Кни́га, яку́ ти пора́див, мені́ ду́же сподо́балася.

The book you recommended I liked a lot. — a relative (subordinate) clause, fenced by commas.

The obligatory comma — and the undroppable що

This is the rule English speakers break most. In Ukrainian the comma before a subordinate clause — before що, щоб, коли́, бо, якщо́, який, and the rest — is mandatory, not optional. English lets you write "I think that he's right" with or without a comma, and even drop "that" entirely ("I think he's right"). Ukrainian does neither: the comma is always there, and що is never dropped.

So "I know you're right" cannot be Я зна́ю ти ма́єш ра́цію. It must be *Я зна́ю, що ти ма́єш ра́цію — with both the comma and the overt що. Every embedded clause is comma-marked and overtly introduced.

💡

Two non-negotiables in Ukrainian complex sentences: (1) put a COMMA before що/щоб/коли́/бо/якщо́/який — always; (2) never drop the complement що. English 'I know you're right' must become Я зна́ю, що ти ма́єш ра́цію — comma in, що in.

When the subordinate clause comes first, the comma sits between the two clauses just the same:

Якщо́ бу́де дощ, ми залиши́мося вдо́ма.

If it rains, we'll stay home. — subordinate clause first; the comma falls between the clauses.

Коли́ всі зібра́лися, ми поча́ли вече́рю.

When everyone had gathered, we started dinner. — fronted time clause, comma after it.

The що-complement after verbs of saying, thinking, knowing

A huge share of complex sentences are complement clauses: after a verb of saying, thinking, knowing, feeling (ка́жуть, ду́маю, зна́ю, ві́рю, споді́ваюся, чу́ю), Ukrainian attaches the reported content with що "that" — and, again, never drops it. This is also the backbone of reported speech.

Ка́жуть, що за́втра поте́плішає.

They say it'll warm up tomorrow. — Ка́жуть, що…, the reported-content clause.

Ду́маю, що ти ма́єш ра́цію, але́ переві́рмо ще раз.

I think you're right, but let's double-check. — Ду́маю, що… with the obligatory comma and overt що.

Споді́ваюся, що все́ бу́де до́бре.

I hope everything will be fine. — Споді́ваюся, що…, complement clause.

Asyndetic (comma-only) sentences

Ukrainian also joins clauses with no conjunction at all — just punctuation. These are asyndetic (безсполучнико́ві) sentences, where a comma, a dash, or a colon does the linking work. A comma lists parallel facts; a dash often signals a result or a sharp contrast; a colon introduces an explanation.

Прийшла́ весна́, розта́нув сніг, защебета́ли пта́хи.

Spring came, the snow melted, the birds began to sing. — asyndetic: three clauses joined by commas alone, no conjunction.

Не поспіша́й — все́ ще всти́гнемо.

Don't rush — we'll still make it in time. — asyndetic with a dash signalling the consequence.

Source-language comparison

For an English speaker, two habits to break. (1) The comma is mandatory. English treats the comma before "that / when / because" as optional or even wrong; Ukrainian requires it before що, щоб, коли́, бо, якщо́, який — every time. (2) що is never dropped. English freely deletes the complement "that" ("I know you're right"); Ukrainian keeps it — Я зна́ю, що ти ма́єш ра́цію. Also note that English "but" splits into Ukrainian а (soft, "whereas") and але́ (sharp, "but"), and "and" can be і / й (й after a vowel) or та.

For a Russian speaker, the framework is familiar but the words are Ukrainian: the complement is що (not что), purpose is *щоб (not *чтобы), "because" is бо / тому́ що, the relativizer is яки́й (not *который), and "and/whereas" contrast uses а. The obligatory-comma rule matches Russian; keep it.

Common Mistakes

❌ Я зна́ю ти ма́єш ра́цію.

Missing comma and missing що — Ukrainian keeps both: Я зна́ю, що ти ма́єш ра́цію.

✅ Я зна́ю, що ти ма́єш ра́цію.

I know you're right — comma + overt що, both obligatory.

❌ Ду́маю що за́втра бу́де дощ.

The comma before що is obligatory: Ду́маю, що за́втра бу́де дощ.

✅ Ду́маю, що за́втра бу́де дощ.

I think it'll rain tomorrow — comma before the complement clause.

❌ Я чита́ю а він спить.

A compound sentence needs a comma before а: Я чита́ю, а він спить.

✅ Я чита́ю, а він спить.

I'm reading, whereas he's sleeping — comma before the coordinator а.

❌ Хочу́ піти́, а не мо́жу.

A sharp 'but' / obstacle is але́, not а: Хочу́ піти́, але́ не мо́жу.

✅ Хочу́ піти́, але́ не мо́жу.

I want to go, but I can't — але́ for a real obstacle.

❌ Зателефону́й мені́ якщо́ щось зміни́ться.

The comma before якщо́ is obligatory: Зателефону́й мені́, якщо́ щось зміни́ться.

✅ Зателефону́й мені́, якщо́ щось зміни́ться.

Call me if anything changes — comma before the condition clause.

Key Takeaways

Simple = one clause; compound (складносуря́дне) = equal clauses joined by і/й, та, а, але́, або́; complex (складнопідря́дне) = main + subordinate clause via що, щоб, коли́, бо, якщо́, який.
The comma before every subordinator and relativizer (and between compound clauses) is obligatory — unlike English's optional comma.
The complement що is never dropped: 'I know you're right' = Я зна́ю, що ти ма́єш ра́цію.
"But" splits: а (soft, 'whereas') vs але́ (sharp 'but'); "and" = і/й (й after a vowel) or та.
Clauses can also join asyndetically — by a comma, dash, or colon alone, with no conjunction.

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