To talk about a finished past action, put -i- between the verb stem and the personal ending: ostan becomes ostin (I bought). The he/she form takes no ending at all, just the -i-: osti. Some stems change shape when the -i- is added, as in syödä - söin.
Examples
- Ostin torilta vihanneksia.
- I bought vegetables at the market.
- Hän osti uuden auton.
- He/she bought a new car.
- Söimme eilen hyvän illallisen.
- We ate a good dinner yesterday.
- Mitä sinä teit eilen?
- What did you do yesterday?
The mistake to avoid
The negative past does not use -i-: say 'en ostanut mitään' (I didn't buy anything), never 'en ostin'.
Where this fits in
Menneisyys ja viime viikonloppu, Finnish A2: Talk about the past: yesterday, last weekend, and travel memories.