-isi-

The conditional mood is one of the most versatile tools in Finnish. Here is how to build and use it:

1. Formation
The marker -isi- is added to the vowel stem of the verb. In verbs with present-tense direct gradation, the active conditional uses the strong stem (e.g., antaa → antaisin), unlike the 1st and 2nd person present tense of Type 1 verbs.

• Stem Vowel Changes: If the stem ends in -e or -i, that vowel is dropped before adding -isi- (luke- → lukisin, etsi- → etsisin). Short final vowels like -a, -ä, -o, -u, and -y are always kept when adding the conditional marker (anta- → antaisin, puhu- → puhuisi).
• Long Vowels and Diphthongs: To avoid three vowels in a row, one vowel is dropped. For long vowels (like aa), the second vowel is removed (saada → saisin). For diphthongs ending in -o, -ö, or -e (uo, yö, ie), the first vowel is removed (syödä → söisin, viedä → veisin). A notable exception is the common verb käydä, which changes to kävisin.

2. Hypothetical Situations
A hypothetical condition and its consequence commonly both use the conditional.
Example: Jos minulla olisi rahaa, ostaisin auton. (If I had money, I would buy a car.)

3. Politeness
Using the conditional makes requests softer. Voisitko auttaa? (Could you help?) is more tentative than Voitko auttaa? (Can you help?). Both can be natural and polite; context and tone matter.

4. Negative Conditional
The negative conditional is formed using the negative verb (en, et, ei, emme, ette, eivät) followed by the conditional stem without personal endings. Example: en antaisi (I would not give).

5. Past and Passive Forms

• Past Conditional: Formed using the conditional of olla (olisin, olisit...) and the past participle. Example: Olisin tullut, jos olisin voinut. (I would have come if I had been able to.)
• Passive Conditional: The most reliable way to form the passive conditional is to take the past passive (e.g., puhuttiin), drop the -iin, and add -aisiin / -äisiin (yielding puhuttaisiin). In spoken Finnish, the passive conditional is the standard way to say 'we would' (e.g., Me puhuttaisiin instead of Me puhuisimme).

6. Personal Endings and Spoken Finnish
The conditional uses the standard personal endings. Note that the 3rd person singular (hän) has no extra ending after -isi. Spoken forms vary: final i can disappear (menisi → menis), and olisi can become ois. First-person mä menisin, sometimes with a weakened final n, also occurs; forms without that n are regional or colloquial variants, not a requirement for every singular person.