Questions & Answers about Umferðin minnkar oft seint á kvöldin.
The ending -in is the suffixed definite article, so umferðin means the traffic.
A few useful points:
- Icelandic usually attaches the to the end of the noun instead of putting a separate word in front.
- umferð = traffic
- umferðin = the traffic
Here, umferðin is the nominative singular definite form.
Also, Icelandic sometimes uses the definite form in places where English would just say traffic with no article. A bare umferð is also possible in some contexts, but umferðin sounds like the traffic in the situation being discussed.