Questions & Answers about Ruuhka vähentyy illalla.
Ruuhka literally means congestion, traffic jam, or rush‑hour traffic.
In this short, generic sentence, ruuhka is best understood as the rush‑hour traffic / the traffic congestion in general, not one specific jam.
Compare a few uses:
- Tiellä on ruuhka. – There is a (bad) traffic jam on the road.
- Aamulla on kova ruuhka. – In the morning there is heavy rush‑hour traffic.
So the word itself is singular, but depending on context it can refer to:
- one specific jam, or
- the general state of congestion, like in the target sentence.
Finnish simply does not have articles like a/an or the.
- Ruuhka vähentyy illalla.
→ could be translated as The traffic decreases in the evening or Traffic gets lighter in the evening.
Whether you understand it as the traffic, rush‑hour traffic, or just traffic in general comes entirely from context, not from any special word in Finnish.