DA-KOMPOSITA

Da-compounds are essentially shortened versions of a prepositional phrase.
They may only be used when the object of the preposition is not a person.
Use the preposition given and add a da(-r-).  "r" is necessary before prepositions beginning with a vowel.
 

                    Schläft die Katze auf dem Bett?  Ja, sie schläft darauf.

   Using the same preposition (in this case, "auf") you can form a da-compound da-r-auf because "Katze" is not a person.
 

Note:  There are two da-compounds that have idiomatic meanings:

 dabei = on or with someone  Ich habe Geld dabei.  [I have money with me.]

 darum = that's why   Ich habe die Zeitung gelesen.  Darum weiß ich von
      dem Orkan.  [I read the paper.  That's why I know
      about the hurricane.]
 
 
 
 

When a person is the object of the preposition, it must be replaced with a personal pronoun of the appropriate case
(according to the preposition), number and gender (according to the object of the preposition.

                    Ich wohne noch bei meinen Eltern. --   Ich wohne noch bei ihnen.
                                              Dative/Plural                                                  Dative/Plural