An if-sentence has two halves: the condition (the jos clause) and the consequence (the main clause). The single most important thing to understand about Finnish here is that jos does not decide the mood. Unlike some languages where "if" mechanically triggers a special verb form, Finnish chooses the mood by asking a real question: is this situation genuinely possible, or is it merely hypothetical? Get that judgement right and the verb forms follow automatically. This page covers the tense-and-mood pairing across the three standard sentence types; how to build the -isi- forms themselves is on the conditional formation page, and more elaborate jos/ellei/kunhan syntax is on the conditional sentences page.
Type 1: real / open conditions — present in both clauses
When the condition is genuinely possible — it might well happen — Finnish uses the present tense in both halves. There is no conditional anywhere. This is the "if X happens, Y happens" of plans, rules, and predictions.
Jos sataa, jään kotiin.
If it rains, I'll stay home. (a real possibility)
Jos ehdit, soita minulle.
If you have time, call me. (present condition, imperative consequence)
Jos et syö nyt, ruoka jäähtyy.
If you don't eat now, the food will get cold.
Note that the consequence can be a command (soita!) or a negative — the point is only that the jos clause stays in the plain present, because the rain, the free time, and the eating are all real prospects.
Type 2: unreal / hypothetical conditions — conditional in BOTH clauses
When the condition is contrary to fact or purely imagined — you are dreaming, supposing, or being tactful — Finnish puts the conditional (-isi-) in both halves. This is where English speakers stumble, so look closely at the contrast:
Jos sataa, jään kotiin.
If it rains, I'll stay home. (real — it may actually rain)
Jos sataisi, jäisin kotiin.
If it were raining, I'd stay home. (hypothetical — it isn't raining)
Both verbs carry -isi-: sataisi and jäisin. English, by contrast, deliberately mismatches its two halves — "if I had time, I would travel" uses a past tense after if but would in the main clause. Finnish does the opposite: it echoes the same mood in both clauses. Whatever mood the jos half is in, the main half matches it.
Jos minulla olisi aikaa, matkustaisin enemmän.
If I had time, I'd travel more.
Jos tulisit käymään, olisin todella iloinen.
If you came to visit, I'd be really happy.
Jos voittaisin lotossa, ostaisin talon meren rannalta.
If I won the lottery, I'd buy a house by the sea.
Type 3: past counterfactuals — perfect conditional in both clauses
To talk about what would have happened — a situation that is over and turned out otherwise — use the perfect conditional in both halves. The perfect conditional is olla in the conditional (olisin, olisit, olisi...) plus the past participle (-nut/-nyt/-neet). Details are on the perfect conditional page; here notice only that, once again, both clauses take the same form.
Jos olisin tiennyt, olisin tullut.
If I had known, I would have come.
Jos olisit soittanut, olisin voinut auttaa.
If you had called, I could have helped.
Jos et olisi myöhästynyt, olisimme ehtineet junaan.
If you hadn't been late, we'd have made the train.
English here uses the pluperfect after if ("if I had known") and would have in the main clause — another mismatch. Finnish keeps both halves in the identical perfect conditional: olisin tiennyt ... olisin tullut.
The summary table
| Type | jos clause | main clause | Example |
|---|---|---|---|
| Real / open | present | present (or imperative) | Jos sataa, jään kotiin. |
| Unreal / hypothetical | conditional -isi- | conditional -isi- | Jos sataisi, jäisin kotiin. |
| Past counterfactual | perfect conditional | perfect conditional | Jos olisin tiennyt, olisin tullut. |
Common Mistakes
❌ Jos minulla oli aikaa, matkustaisin.
Incorrect — copying English 'if I had time' with a past tense; a hypothetical needs the conditional in BOTH clauses.
✅ Jos minulla olisi aikaa, matkustaisin.
If I had time, I'd travel.
❌ Jos sataisi, jään kotiin.
Incorrect — the halves don't match; the conditional in the jos clause requires the conditional in the main clause.
✅ Jos sataisi, jäisin kotiin.
If it were raining, I'd stay home.
❌ Jos tiesin, olisin tullut.
Incorrect — a past counterfactual needs the perfect conditional, not the plain past, in the jos clause.
✅ Jos olisin tiennyt, olisin tullut.
If I had known, I would have come.
❌ Jos olisin tiennyt, tulisin.
Incorrect mixing — a past counterfactual keeps the perfect conditional in BOTH clauses, not a simple conditional in the main clause.
✅ Jos olisin tiennyt, olisin tullut.
If I had known, I would have come.
Key Takeaways
- Jos does not choose the mood — the reality of the situation does. The same conjunction heads all three sentence types.
- Real/open: present + present — Jos sataa, jään kotiin.
- Hypothetical: conditional -isi- in both clauses — Jos sataisi, jäisin kotiin.
- Past counterfactual: perfect conditional (olisin
- -nut) in both clauses — Jos olisin tiennyt, olisin tullut.
- Finnish matches its two halves; English deliberately mismatches them (past + would). Never carry the English split into Finnish.
Now practice Finnish
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Start learning Finnish→Related Topics
- The Conditional -isi-: 'would'A2 — Meet the Finnish conditional mood — the -isi- marker that packs English 'would' inside the verb (puhuisin, tulisi, olisi) for hypotheticals, wishes and politeness.
- Forming the ConditionalB1 — Build -isi- forms across all verb types: strong grade throughout, -e drops, long vowels contract (saada→saisin, tehdä→tekisin), short -a/-ä stays (antaisin).
- The Perfect Conditional: olisin tehnytB2 — The Finnish 'would have': olla in the conditional plus the past participle (olisin tehnyt) for counterfactual past — things that would have happened but didn't.
- Conditional Sentences: Real and UnrealB2 — The three jos-patterns: real conditions (present + present), unreal present (conditional in both clauses), and unreal past (perfect conditional), plus ellei.