Questions & Answers about Minä istun autossa, kunnes valo vaihtuu.
Does the word kunnes change the word order of the clause that follows it?
No, kunnes introduces a subordinate clause, which usually follows the standard Subject-Verb order in Finnish. You can see this here with the subject valo coming right before the verb vaihtuu. Unlike some other European languages, Finnish doesn't push the verb to the end of the sentence after conjunctions.
Why do we need a comma before kunnes?
In Finnish punctuation rules, you almost always put a comma between a main clause (Minä istun autossa) and a subordinate clause. Since kunnes introduces a subordinate clause, the comma is mandatory here.
Why is the verb vaihtuu used here instead of the more common verb vaihtaa (to change)?
Vaihtua is an automative (intransitive) verb, meaning something changes on its own or undergoes a change. Vaihtaa is transitive, meaning somebody actively changes something (like changing your clothes). Because the traffic light changes by itself, you must use vaihtuu.
The light changing is a future event. Why are both verbs (istun and vaihtuu) in the present tense?
Finnish doesn't have a dedicated future tense. The present tense forms handle both what you are doing right now (Minä istun) and what is going to happen soon (valo vaihtuu). The conjunction kunnes creates the timeline, making it perfectly clear that the light changing is an upcoming event.