Questions & Answers about Odotin, kunnes juna tuli.
Why does odotin only have one t when the dictionary form is odottaa?
This happens because of consonant gradation. When you add the -n ending for "I", the syllable becomes closed, which weakens the strong double tt into a single t. The i before the n is the past tense marker.
I learned that asti means "until". Why use kunnes here?
You use kunnes to connect two full clauses (meaning both sides have a verb, like "I waited" and "the train came"). You use asti when linking "until" to a noun, like huomiseen asti (until tomorrow) or loppuun asti (until the end).
The verb odottaa usually requires an object in the partitive case. Why is juna in the nominative (basic) form?
Because juna is the subject of the second half of the sentence (juna tuli), not the direct object of your waiting. If you simply said "I waited for the train", it would be Odotin junaa (partitive). But here, the train is the one doing the action of coming!
Is the comma before kunnes mandatory?
Yes. In Finnish, when a sentence contains two separate clauses that both have their own verb (here, odotin and tuli), you almost always separate them with a comma.