When can one omit the indefinite article?

Question

New to German here (via Duolingo, DW and other sources), and I'm confused about when indefinite articles in singular objects can/should be omitted. For instance, on Duolingo, "I have a bicycle" was introduced as "Ich habe Fahrrad", but in the sentence, Meine Tante hat ein Fahrrad, aber sie fährt gern Motorrad, omitting the ein is marked wrong.

I saw someone mention that some verbs (like fahren) omit the indefinite article, but then I came across these:

• "We're taking a break" => Wir machen Pause
• "We're having a party" => Wir machen eine Party

What's the rule?

Answer 1

When using the indefinite article, you are referring to a specific thing. Without indefinite article, you are referring to the concept of the thing. Example:

• Wir machen eine Party. (We are having a specific party that we are organizing.)

• Wir machen Party. (We are partying. There doesn't need to be a specific party, we are just doing things that one would do at a party.)

• Wir machen eine Pause. (We are take a specifc break, at a specific time.)

• Wir machen Pause. (We take breaks. We aren't referring to a specific break, we are just stating that we generally take breaks/a break.)

"Meine Tante hat ein Fahrrad, aber sie fährt gern Motorrad" means my aunt owns a (one specific) bicycle, but she like to drive motorbikes in general (without specifying if she actually owns or uses a specific motorcycle).

In this sense "Ich habe Fahrad", could mean "I own something that represents the concept of a bicycle", but without more context that doesn't really make sense.

One example where this was used (although probably leaving out the definite instead of the indefinite article), was the newspaper headline "Wir sind Papst!" ("We are pope.").

One more thing: Just because these sentences are present tense, doesn't mean the described action is happening right now, but just that these are facts that have happened or will happen.

Answer 2

When you omit an article you can't tell if a definite or an indefinite has been omitted. That is why experts often use the term "null article" if an article (or another determiner) is expected to be there but isn't.

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Null article for categories

When the noun does not name a single item (may it be a defined or an undefined single item) but a category, then you don't use an article:

Ich trinke Bier.
^{I drink beer.}

There is no article, because here Bier/beer is not a glass of beer or a bottle of beer, but a category.

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Indefinite article for a single item that is not specified

Was machst du gerade? Trinkst du ein Glas Wein? - Nein, ich trinke ein Bier.
^{What are you doing now? Are you drinking a glass of wine? - No, I'm drinking a beer.}

Here you signal, that you are drinking one glass or one bottle of beer. And because the semantic focus is not on the number of drinks, but on the kind of beverage, the word ein/one can't be interpreted as a numeral but as an indefinite article.

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Definite article for a single specified item

Ich habe dir ein Glas Wasser und eine Flasche Bier hingestellt. Was davon trinkst du gerade? - Ich trinke das Bier.
^{I put a glass of water and a bottle of beer in front of you. Which one are you drinking now? - I'm drinking the beer.}

Here it is not any beer but the special bottle of beer that is on the table. So you need the definite article here.

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correct: Ich mache Pause.

Here the noun Pause names a category, so this is ok.

correct: Ich mache Party.

category again.

correct: Ich fahre Motorrad.

Again, you are not talking about a single motorbike but about the category.

But this is wrong:

wrong: Ich habe Fahrrad.

You can't own a category. You only can own a single bicycle. So, you must use an article here:

correct: Ich habe ein Fahrrad.

Answer 3

For me, the main question is about the integration of a noun, as RoToRa said, into a superior concept (as a gedankliche Vorstellung), maybe a predicate (Rad fahren, old orthography radfahren), a "Funktionsverbgefüge" (in Gang kommen), or an adverbial expression (zu Fuß, über Nacht, nächste Woche, Mitte April).

There are lots of common verbal phrases without an article:

with haben: jemand hat Fieber / Schnupfen / Grippe / Diabetes / Hunger / Lust (auf) / Angst (vor) / Mut / Besuch / Feierabend / Urlaub / Erfolg / Geburtstag / von etwas Ahnung / ...

with machen: jemandem Platz machen / Essen, Frühstück machen / Feuer machen / Gewinn machen / jemandem Freude machen / jemandem Mühe, Hoffnung, Schande, Stress ... machen / klar Schiff machen / Karriere machen ...

and with many other verbs.

Unfortunately, there is a an equal or even larger number of concepts realised with the definite or indefinite article:

with haben: einen Vogel haben (to be crazy), das Sagen haben (to be the top dog), die Wahl haben (to have the option), eine Stelle haben (to hold a situation) ...

with machen: einer Sache ein Ende machen, ein Gesicht machen, ein Foto machen, eine Aussage machen (to make a declaration), jemandem eine Szene machen ...

and with an uncountable number of other verbs.

I think, as a beginning German learner you have no other choice than learning by heart a certain stock of those expressions before recognizing the underlying principles.

There is a certain tendency in nowadays western colloquial German to create new concepts by dropping any article. They are not standard German:

Hast du Führerschein? | Ich habe morgen Prüfung. | Er hat B1. | Sie trägt nicht gerne Rock. | Brille steht dir nicht. | Sie hat Familie in den USA. | Fahr du mit dem Fahrstuhl, ich laufe Treppe. | Er hat jetzt wieder Arbeit. | Diese Woche hab' ich Frühdienst / bin ich auf Spätschicht. | Der Nico fährt ständig Bleifuß. | Um fünf bin ich noch auf Arbeit. | Habt ihr hier WLAN / Internet / WiFi?

Party machen is one of those relatively new phrases without an article. In my youth in the seventies we didn't say Party but Fete, but I don't remember a verbal phrase Fete machen.

The phenomenon of integrating two or three nouns by 'Artikellosigkeit' into one concept is well known in 'Zwillingsformeln':

Er hatte sein gesamtes Hab und Gut zurücklassen müssen,

sein Hab und Gut being an idiomatic binomial pair meaning his belongings.

Sie wanderte 10 Tage mit Mann und Kind durch den Schwarzwald,

giving the unified idea of the whole family. This is not a lexicalized idiom, you are free to create such phrases ad libitum:

Er hatte Schreibblock und Kugelschreiber (= sein Schreibzeug) / Geld und Kreditkarte (= Zahlungsmittel) dabei. Sie erschien in Jeans und T-Shirt (= unpassend angezogen) zur Beerdigung.