Ob wir heute vegan oder nur vegetarisch kochen, entscheidet meine Schwester erst am Abend.

Here ob means whether.

It introduces an indirect yes/no question, not a normal statement. The idea is:

• Ob wir heute vegan oder nur vegetarisch kochen = Whether we cook vegan or only vegetarian today

German often uses ob where English uses whether or sometimes if.

Examples:

• Ich weiß nicht, ob er kommt. = I don’t know whether he’s coming.
• Sie entscheidet, ob wir gehen. = She decides whether we go.

In your sentence, the speaker is talking about the decision itself, not asking a direct question.

Because ob wir heute vegan oder nur vegetarisch kochen is a subordinate clause.

In German subordinate clauses, the conjugated verb usually goes to the end. Here, kochen is the conjugated verb for wir.

So the order is:

• ob
• wir
• heute
• vegan oder nur vegetarisch
• kochen

That final verb position is one of the most important patterns in German subordinate clauses.

Because the sentence begins with the subordinate clause, and that whole clause takes up the first position in the sentence.

German main clauses follow the verb-second rule. That means the conjugated verb of the main clause must come in the second position.

Structure here:

1. Ob wir heute vegan oder nur vegetarisch kochen = first position
2. entscheidet = verb in second position
3. meine Schwester = subject
4. erst am Abend

So even though meine Schwester is the subject, it comes after the verb because the first slot is already occupied.

The first clause, Ob wir heute vegan oder nur vegetarisch kochen, is a content clause. It expresses what is being decided.

You can think of it as the thing the sister is deciding:

• She decides whether we cook vegan or only vegetarian today.

A more neutral word order would be:

• Meine Schwester entscheidet erst am Abend, ob wir heute vegan oder nur vegetarisch kochen.

That version may be easier to recognize at first, because the main clause comes first.

Because in German, a subordinate clause is separated from the main clause by a comma.

So:

• Ob wir heute vegan oder nur vegetarisch kochen, entscheidet meine Schwester erst am Abend.

This comma is required in standard German.

Erst here means something like not until.

So:

• erst am Abend = not until the evening

It suggests that the decision happens relatively late.

Compare:

• am Abend = in the evening
• erst am Abend = not until the evening

So the sentence has the nuance that the sister won’t decide before then.

Because German often uses the present tense to talk about the near future, just like English often does.

So:

• wir kochen heute can mean we are cooking today or we will cook today, depending on context.

You do not need a future form here. The word heute already gives the time reference.

• vegan = vegan
• vegetarisch = vegetarian

The word nur means only / just.

So:

• vegan oder nur vegetarisch means vegan or only vegetarian

That suggests a contrast:

• vegan is the stricter option
• nur vegetarisch is the less strict option

The nur adds a nuance like:

• maybe not fully vegan, but at least vegetarian

Yes. Ob often introduces an indirect question about which of two possibilities is true.

So:

• ob wir heute vegan oder nur vegetarisch kochen

means:

• whether we cook vegan or only vegetarian today

The oder gives the alternatives inside the ob-clause.

This is very common in German:

• Ich weiß nicht, ob er heute oder morgen kommt.
• Sie überlegt, ob sie bleibt oder geht.

Yes, absolutely.

A very common version would be:

• Meine Schwester entscheidet erst am Abend, ob wir heute vegan oder nur vegetarisch kochen.

This means the same thing.

The original sentence puts the ob-clause first for emphasis or style. Fronting that clause highlights the undecided issue itself.

Not exactly.

• am Abend = in the evening / this evening in a specific situation
• abends = in the evenings or in the evening as a habitual/general time

In your sentence:

• erst am Abend refers to this particular evening, so am Abend is the natural choice.

If you said abends, it could sound more habitual, as if this is what she generally does.

Because here vegan and vegetarisch are being used like adverbial/predicative descriptions of how you cook, not as nouns.

So:

• vegan kochen = to cook vegan food / to cook in a vegan way
• vegetarisch kochen = to cook vegetarian food / to cook in a vegetarian way

This is normal in German. You do not need an article here.

The grammatical subject of the main clause is meine Schwester.

That is why the verb entscheidet is singular:

• entscheidet meine Schwester

Inside the subordinate clause, the subject is wir:

• ob wir heute vegan oder nur vegetarisch kochen

So the sentence contains two different clauses, each with its own subject:

• wir in the subordinate clause
• meine Schwester in the main clause