A reflexive possessive pronoun is used instead of hans, hendes, dens or dets, when you are talking about the possession of something in the 3rd. person singular, where the subject possesses the item in question.
Again, there is a difference between n-words and t-words.
n-word: sin
t-word: sit
plural: sine
| en kjole | a dreess |
| Hun skal vaske sin kjole. | She has to wash her dress. |
| et hus | a house |
| Hun maler sit hus. | She paints her house. |
| bøger | books |
| Lars har læst alle sine bøger. | Lars has read all his books. |
Comparison:
There is no comparable reflexive possessive pronoun in English.