The conditional

1. Use

1.1. With polite questions, wishes, announcements and advices
Saisinko kysyä jotakin?
= Could I ask something?
Sulkisitko oven?
= Would you close the door?
Joisitko jotakin, kahvia vai teetä?
= Would you drink something, coffee or tea?
Kiitos, ottaisin kupin kahvia.
= Thanks, I would take a cup of coffee.

1.2. With hypothetical sentences
Mitä tekisit, jos sinulla olisi paljon rahaa
= What would you do, if you had a lot of money?
Ehkä minä ostaisin uuden auton.
= Maybe I would buy a new car.

2. Formation

Take the strong stem of the verb (by putting the verb in the 3rd person plural and removing the -vat) + isi + personal ending

Verb 3rd person plural Conditional
soittaa he soittavat minä soittaisin
tehdä he tekevät sinä tekisit
luulla he luulevat hän luulisi
avata he avaavat me avaisimme
häiritä he häiritsevät te häiritsisitte
rohjeta rohkenevat he rohkenisivat

2.1. Vowel changes

If you look at the examples above this closely, you will notice that certain vowels get replaced when adding -isi. Check the vowel changes chapter on the page about the imperfect to see which ones disappear and which ones don't.

3. Negative conditional

Conjugate the negative verb, and take the positive conditional tense without the personal ending.

Positive Negative
minä ostaisin minä en ostaisi
sinä ostaisit sinä et ostaisi
hän ostaisi hän ei ostaisi
me ostaisimme me emme ostaisi
te ostaisitte te ette ostaisi
he ostaisivat he eivät ostaisi