Learn Hardcore German: Was für eine Idee, die Tickets früh zu kaufen!

It’s an exclamation. Was für can introduce both questions and exclamations. Here the exclamation mark and the lack of a finite verb make it an exclamation: Was für eine Idee, …! As a real question you’d have something like: Was für eine Idee hast du?

What does Was für mean compared to welch-?

Was für (ein/eine) means “what a / what kind of.” It’s very common and neutral in tone. Welch- is more formal or stylistic: Welch eine tolle Idee! In everyday speech, Was für eine tolle Idee! is more typical.

Why is it eine Idee and not ein Idee?

Because Idee is grammatically feminine in German, so the indefinite article is eine (not ein). Singular count nouns need an article in this construction.

Does the für in was für force the accusative case?

No. In was für (ein/eine), für is part of a fixed determiner, not the preposition that governs the accusative. The case of the noun phrase is determined by its role in the sentence. Example:

Mit was für einem Plan kommst du? (dative after mit)
Über was für eine Idee sprechen wir? (accusative after über)

What case is eine Idee here?

It’s an elliptical exclamation without a verb, so there’s no syntactic environment to impose a case. Formally it’s case-ambiguous, but you can think of it as nominative by default. With feminine singular, nominative and accusative both look like eine anyway.

What is the function of the comma and the zu-infinitive clause?

The part die Tickets früh zu kaufen is a zu-infinitive group that specifies the content of the noun Idee (apposition: “the idea (namely): to buy the tickets early”). A comma is required because the infinitive group depends on a noun. This follows standard German comma rules.

Why is it zu kaufen and not um … zu kaufen?

Use a bare zu-infinitive to express the content of a noun like Idee/Plan: die Idee, … zu kaufen. Use um … zu for purpose: Wir kaufen die Tickets früh, um Geld zu sparen.

Can I say früh die Tickets zu kaufen instead of die Tickets früh zu kaufen?

Both are possible. Common and slightly more natural is die Tickets früh(zeitig) zu kaufen. Placing früh first (früh die Tickets zu kaufen) can emphasize the earliness. With pronouns, the pronoun typically comes before the adverb: sie früh zu kaufen.

Why die Tickets and not just Tickets?

die Tickets implies specific tickets known in context (e.g., for a concert you’ve been discussing).
If you mean the idea in general, you can drop the article: Tickets früh(zeitig) zu kaufen. Both are possible; choose based on whether the tickets are specific or generic.

Is the die in die Tickets a relative pronoun because there’s a comma before it?

No. Here die is the definite article for the plural noun Tickets inside an infinitive clause. A relative clause would need a finite verb (e.g., …, die wir früh kaufen.), which is not the case here.

Is Tickets the best word, or should I say Karten?

Both are fine. Tickets is widely used and a bit more international/colloquial. Karten (e.g., Eintrittskarten, Kinokarten) is very common too and sometimes sounds more traditionally German. For travel you’ll also hear Fahrkarten. Choose based on context and local preference.

Is the sentence positive or could it be sarcastic?

It’s neutral by itself; the tone of voice or added adjectives make it clear. Positive: Was für eine tolle/gute Idee! Negative/sarcastic: Was für eine blöde/schlechte Idee!

Can I make this a full sentence?

Yes: Es ist (war) eine gute Idee, die Tickets früh(zeitig) zu kaufen. The exclamatory fragment is just a stylistic choice for emphasis.

How do I refer to a completed past action here?

You usually still use the simple zu-infinitive: Es war eine gute Idee, die Tickets früh zu kaufen. A perfect infinitive (… gekauft zu haben) is possible but less common and can sound heavy unless you need to emphasize completion in a more complex sentence.

Do I always need ein/eine after was für?

For singular count nouns, yes: Was für eine Idee!, Was für ein Plan! For plurals or mass nouns, there’s no article: Was für Ideen!, Was für Musik!

Is früh the best word here, or should I use frühzeitig?

Both work. früh = early (in time); frühzeitig = early/with sufficient lead time and often sounds a bit more purposeful or formal. So: die Tickets früh vs die Tickets frühzeitig. Don’t use bald here—bald means “soon,” not “early.”

Is the comma the only punctuation I can use before the infinitive group?

A comma is standard and correct. A colon or dash can be used stylistically to introduce the explanation: Was für eine Idee: die Tickets früh zu kaufen! But in neutral prose, prefer the comma.

Any colloquial variations I might hear?

Yes: Was für ’ne Idee, die Tickets früh zu kaufen! (contracted eine). You might also hear synonyms: So eine gute Idee, … or Eine tolle Idee, …