This is the 46th most frequent Finnish word.
koska
"Koska" means "because" or "when" in English, depending on the context.
Here, 'koska' is used as a subordinating conjunction to express a reason.
Koska sää on kaunis, menemme ulos.
Because the weather is beautiful, we are going outside.
In this sentence, 'koska' means 'when' and is used to indicate a time condition.
Kerro minulle, koska tunnet olosi mukavaksi.
Let me know when you feel comfortable.
Here, 'koska' is again used to mean 'when,' denoting an uncertain future time event.