Three Ways to Say "Because"

Last week, we discussed the differences between denn and dann. This week we are going to look at denn, weil, and da, the most common ways of saying "because" in German. There is a big difference in the way these words affect the sentence structure, however. Without getting too in-depth with complicated grammar rules, we can easily understand that the coordinating conjunction denn does not require that the sentence order of Subject-Verb-Object be changed, but the subordinating conjunctions weil and da do. The German verbs are marked in green so you can note their placement in the sentence:

Solche Bilder sind selten,

Such images are rare,

denn Olme haben nur alle sechs bis acht Jahre Nachwuchs.

because olms have offspring only once every six to eight years.

Caption 33, Alpenseen - Kühle Schönheiten
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The subordinate conjunction weil forces the sentence structure to place the verb at the end of the sentence. Compare the above with how it would read if it used weil or da instead of denn:

Solche Bilder sind selten, weil Olme nur alle 6 bis 8 Jahre Nachwuchs haben.
Solche Bilder sind selten, da Olme nur alle 6 bis 8 Jahre Nachwuchs haben.
Such images are rare, because olms have offspring only every 6 to 8 years.

Note that the English translation is identical. Another example:

Ich übernehm' mal den Part, denn ich bin Pressesprecher.

I will take over this part because I'm the press spokesman.

Caption 5, Die OLElympischen Spiele - Laotischer Hühnertanz
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But this time with weil and da:

Ich übernehme mal den Part, weil ich Pressesprecher bin.
Ich übernehme mal den Part, da ich Pressesprecher bin.
I will take over this part because I'm the press spokesman.

So you see how using denn, the sentence structure remains the same as the standard English Subject-Verb-Object, but with weil and da, the verb must go at the end of the sentence.

The conjunctions denn, weil and da also differ in other ways relating to how each word affects the sentence structure. A clause or sentence part with denn must come after the part of the sentence that it is modifying, so the sentence structure is required to stay like the denn examples above. With weil and da, however, you could structure the examples above three different ways, depending on how you wish to place the emphasis in the sentence:

Solche Bilder sind selten, weil Olme nur alle 6 bis 8 Jahre Nachwuchs haben.
Weil Olme nur alle 6 bis 8 Jahre Nachwuchs haben, sind solche Bilder selten.
Solche Bilder sind, weil Olme nur alle 6 bis 8 Jahre Nachwuchs haben, selten.

Ich übernehme mal den Part, da ich Pressesprecher bin.
Da ich Pressesprecher bin, übernehme ich mal den Part.
Ich übernehme mal, da ich Pressesprecher bin, den Part.

In the above examples, the first sentences are the most commonly seen sentence structure, the second sentences less so, and the last is the least likely, although all three are grammatically correct.

Next week we'll take a look at a fourth way of saying "because," but it's not a conjunction — it's an adverb! Can you guess what it is?

Further Learning
Go to Yabla German and search for denn and weil to see the words used in a real-world context and note how the sentence structure can vary with the two words. For an advanced analysis the conjunctions denn and weil, read this DWDS article on denn and this DWDS article on weil.