Breakdown of Olen aivan samaa mieltä.
olla
to be
sama
same
aivan
exactly / quite (completely)
mieli
mind / opinion (mind, mood)
Questions & Answers about Olen aivan samaa mieltä.
Why is there no verb for 'agree' in this sentence?
Why are the words sama and mieli in the partitive case (samaa mieltä)?
When you express an opinion or abstract state of being with the verb olla (to be), Finnish treats that state as a mass or uncountable amount. You are essentially saying you hold 'some of the same opinion', which triggers the partitive endings.
What does aivan add, and could I use todella instead?
Aivan means 'completely', 'exactly', or 'quite'. It is the most natural word to pair with samaa mieltä to emphasize that you 'completely agree'. While you could technically use todella (really), aivan is the standard, idiomatic choice for this specific phrase.
Since this lesson is about the -kin (also/too) ending, how would I add it to say 'I also completely agree'?
To say 'I also agree' (meaning me, as well as you), you need to bring back the dropped pronoun minä (I) and attach the clitic to it: Minäkin olen aivan samaa mieltä. If you attached it to the verb instead (Olenkin aivan samaa mieltä), it changes the meaning to something closer to 'Actually, I do agree' after a change of heart.