Of vs Als: 'If' = Whether or Condition? | Dutch Grammar

English overloads one little word, if, with two completely different meanings, and most English speakers never notice because they use the same word for both. Compare: "I don't know if he's coming" versus "If it rains, I'll stay home." The first if means whether — it's reporting an unanswered yes/no question. The second if states a condition — it sets up something that may or may not happen. Dutch refuses to blur these. It uses of for the first and als for the second, and choosing wrong is jarring to a native ear. The good news: there's a one-word test that gets it right every time.

The one rule that decides it

Run this test on the English sentence:

Can you replace "if" with "whether" and keep the meaning? → use of. This happens after verbs of not knowing, asking, wondering, doubting, checking: weten, vragen, zich afvragen, twijfelen, kijken, controleren.
Does "if" set up a condition — something that, if true, triggers a result? → use als. You usually can't swap in "whether" here; you could swap in "when" or "in the event that."

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The whether test is foolproof. Say the English sentence out loud with whether instead of if. If it still sounds right ("I don't know whether he's coming"), it's of. If "whether" sounds wrong ("Whether it rains, I'll stay home" — nonsense), it's a condition, so als.

Ik weet niet of hij komt.

I don't know whether/if he's coming. — 'whether' fits, so it's of.

Als het regent, blijf ik thuis.

If it rains, I'll stay home. — a condition; 'whether' would be nonsense, so it's als.

Note that both are subordinating conjunctions, so both send the verb of their clause to the end (of hij komt, als het regent). The verb-final word order is identical — the only thing you're choosing is which word, based on meaning.

Of: 'whether' — indirect yes/no questions

Use of when you're embedding a yes/no question inside a larger sentence. The original question — "Komt hij?" ("Is he coming?") — gets folded into a main clause and introduced by of. This is exactly the English "whether," and of is its only correct translation.

Ik vraag me af of dit wel een goed idee is.

I wonder whether this is really a good idea. — embedded yes/no question: of.

Weet jij of de winkel op zondag open is?

Do you know whether the shop is open on Sundays? — reporting a yes/no question: of.

Ze vroeg of ik kon helpen.

She asked if/whether I could help. — after 'vragen' (to ask), always of.

A reliable signal: of typically follows a verb of knowing, asking, wondering, doubting, or checking. After (niet) weten, vragen, zich afvragen, twijfelen, kijken of, controleren of — it's of every time. The clause after of is the hidden yes/no question.

Ik twijfel of ik wel ga.

I'm not sure whether I'll go. — twijfelen (to doubt) takes of.

You'll also meet of as the everyday word for "or" (koffie of thee? — "coffee or tea?"). That's a separate, coordinating use and doesn't affect word order. Context keeps them apart: between two nouns it's "or"; introducing a whole clause after a verb of asking/knowing, it's "whether."

Als: 'if' — real conditions

Use als when if introduces a condition: a situation that may or may not hold, with a consequence attached. Als X, (dan) Y = "if X, (then) Y." You can almost always paraphrase it in English with "in the event that" or, for repeated/general situations, "when."

Als je honger hebt, is er soep in de keuken.

If you're hungry, there's soup in the kitchen. — a condition, so als.

Ik bel je als ik thuis ben.

I'll call you when/if I'm home. — condition/time; als (here it also covers English 'when' for future events).

When the als-clause comes first, the main clause inverts (verb before subject), and you'll often see an optional dan ("then") marking the result. This is the same inversion you get whenever a subordinate clause opens a Dutch sentence.

Als het morgen mooi weer is, dan gaan we naar het strand.

If the weather's nice tomorrow, (then) we'll go to the beach. — als-clause first; main clause inverts to 'gaan we'.

Je mag mijn fiets lenen als je voorzichtig bent.

You can borrow my bike if you're careful. — condition; als-clause second this time.

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Watch out: Dutch als covers English "if" (condition) and English "when" for repeated or future events (Als ik wakker word, drink ik koffie = "When I wake up, I drink coffee"). For a single past event, Dutch switches to toen — but that's a separate page. Here, just remember: condition or general/future "when" → als.

The two side by side

This minimal pair shows the whole distinction in one breath:

Ik weet niet of hij komt.

I don't know whether he's coming. — reporting an open question: of.

Ik ben blij als hij komt.

I'm happy if/when he comes. — a condition with a consequence: als.

Same three-word tail (hij komt), opposite meanings. Of hij komt leaves it genuinely unknown; als hij komt sets up "in the event he comes." English would use "if" for both, which is exactly why this trips people up.

	of	als
English meaning	whether (indirect yes/no question)	if (condition) / when (future, general)
"Whether" test	passes	fails
Typical trigger	weten, vragen, zich afvragen, twijfelen	a condition + a consequence
Verb position	final	final
Example	Ik weet niet of hij komt	Als hij komt, …

Common Mistakes

These errors come straight from English using one word, "if," for both jobs.

❌ Ik weet niet als hij komt.

Incorrect — this is an indirect yes/no question ('whether'), so it must be of, not als.

✅ Ik weet niet of hij komt.

I don't know whether he's coming.

❌ Ik vraag me af als het waar is.

Incorrect — 'I wonder whether…' is an embedded question, so use of.

✅ Ik vraag me af of het waar is.

I wonder whether it's true.

❌ Of je honger hebt, is er soep.

Incorrect — this is a condition ('if you're hungry'), so use als, not of.

✅ Als je honger hebt, is er soep.

If you're hungry, there's soup.

❌ Ze vroeg als ik kon helpen.

Incorrect — after 'vragen' (to ask) reporting a yes/no question, it's of.

✅ Ze vroeg of ik kon helpen.

She asked whether I could help.

❌ Ik bel je of ik thuis ben.

Incorrect — this is a condition/time ('when I'm home'), so use als. 'Of ik thuis ben' would mean 'whether I'm home'.

✅ Ik bel je als ik thuis ben.

I'll call you when I'm home.

Key Takeaways

of = "whether" — indirect yes/no questions, after weten, vragen, zich afvragen, twijfelen. Apply the whether test: if "whether" fits, use of.
als = "if" (a condition) and also "when" for future or repeated events.
Both are subordinating, so both put the verb last; you're only choosing the word, by meaning.
When an als-clause leads, the main clause inverts and often takes optional dan.
Of also means plain "or" between two options — different use, no word-order effect.

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