Coordinating conjunctions

The main clause of a German sentence contains a subject and a verb and makes complete sense when it stands alone. Except when some element other than the subject begins a main clause, the subject precedes the verb:

Er kommt spät nach Hause.                 He comes home late.

Tina versteht es nicht.                           Tina doesn’t understand it.

Setz dich hin! (Du is understood.)     Sit down.

This word order is important when using coordinating conjunctions.
Coordinating conjunctions

Coordinating conjunctions can link together words, phrases, or even complete sentences (
main clauses):
word    + conjunction + word
phrase + conjunction + phrase
clause  + conjunction + clause

The most commonly used coordinating conjunctions are:
aber                                                        but
denn                                                       because, for, since
oder                                                        or
sondern (used with nicht or kein)   but (rather)
und                                                         and
When combining sentences with these conjunctions, a comma is used to mark off the two clauses. With und and sometimes with aber, however, this is optional. If the combination of two clauses with und is confusing, a comma can precede und for the sake of clarity.
Let’s look at some example sentences that illustrate the use of coordinating conjunctions:

Der Mann klopfte laut an die Tür,                     The man knocked loudly on the door,

   aber niemand war zu Hause.                           but no one was home.

Sie ging nicht zur Schule, denn                          She didn’t go to school, because she

   sie war wieder krank.                                        was sick again         

Du darfst hier übernachten, oder                       You can stay here overnight, or we can 

wir können ein Hotel für dich finden.               find a hotel for you.

Ich habe keinen Artikel gefunden, sondern    I didn’t find an article, but I bought a whole      ich habe ein ganzes Buch über sein                   book about his life
Leben gekauft.
Vater schläft auf dem Sofa und Mutter            Father is sleeping on the sofa, and mother is
arbeitet in der Küche.                                            working in the kitchen.

sentence 1 + comma + coordinating conjunction + sentence 2
Er bleibt zu Hause + , + denn + er ist krank.

He’s staying home, because he’s sick.

  When the subject of the first clause is identical to the subject of the second clause, it is possible to omit the second subject and sometimes even the verb. For example:
Wir können bei Inge übernachten, oder          We can stay overnight at Inge’s or find a hotel.
ein Hotel finden.
Vater kann nicht schlafen und arbeitet in       Father can’t sleep and is working in the 
der Küche.                                                              kitchen.
This is especially true of sondern:
Erik ist nicht eingeschlafen, sondern hat     Erik didn’t fall asleep but rather thought about
die ganze Nacht an Tina gedacht.                  Tina all night.
Ich habe keinen Artikel gefunden,                 I didn’t find an article but bought a whole book
sondern ein ganzes Buch über sein                about his life.
Leben gekauft.
  These five conjunctions are unique in that they require no word order change. The standard word order for a declarative, interrogative, or imperative sentence is used in both clauses that surround a coordinating conjunction.