When describing a bustling scene like a busy harbor dockside, you often need to point out people or things performing actions for the first time (using "a" or "some").
In Danish, there is a strong stylistic preference against starting a sentence with an indefinite subject. While a sentence like "A woman is mooring the ferry" is perfectly normal in English, putting en kvinde at the very start of an active Danish sentence can sound awkward.
The Presentational Construction
To solve this, Danish uses a presentational relative clause. You introduce the indefinite subject with der er (there is / there are), and then immediately follow it with the relative pronoun der (who / which / that) and the rest of the action.
Instead of saying "A woman is mooring the ferry", you literally say "There is a woman who is mooring the ferry":
| There is a woman who is mooring the ferry at the dock. | Der er en kvinde der fortøjer færgen ved kajen. |
This pattern works exactly the same for plural indefinite subjects, like mange havnearbejdere (many dockers) or en mand (a man):
| There are many dockers who are carrying the heavy freight. | Der er mange havnearbejdere der bærer den tunge fragt. |
| There is a man mooring the rocking boat with a rope. | Der er en mand der fortøjer den gyngende båd med et tov. |
Questions and Negations
You can easily turn this structure into a question by inverting the first verb and subject to er der:
| Is there a fisherman repairing the big net? | Er der en fisker der reparerer det store net? |
It is also extremely common to use this construction with negative indefinite subjects, such as ingen (no / none):
| There are almost no fishermen who are working here today. | Der er næsten ingen fiskere der arbejder her i dag. |
Definite Subjects
Remember that this der er ... der workaround only exists to avoid starting sentences with indefinite subjects. If your subject is definite (the fisherman, the girl), it is perfectly fine to place it right at the beginning of the sentence normally.
| The fisherman pulls the big net up onto the dock. | Fiskeren trækker det store net op på kajen. |
| The girl on the dock likes the smell of the sea. | Pigen på kajen kan lide lugten af havet. |