-i- (imperfektin tunnus)

The imperfect locates a situation in the past; the action can be completed, ongoing at that past time, or repeated. It does not itself state whether the result still matters now. It is the most common past tense in Finnish.

1. Formation with -i-
For most verb types, the marker -i- is added to the inflectional stem. For example:

• puhua (to speak) → puhu- + -i- + -n = puhuin (I spoke)
• valita (Type 5) → valitse- (stem) → drops 'e' + -i- + -n = valitsin (I chose)

2. Formation with -si-
Verbs in Type 4 use the marker -si- instead of just -i-. Additionally, some Type 1 verbs ending in -taa/-tää or -tea/-teä (preceded by l, n, r, or a vowel) change the t to s:

• haluta (Type 4) → halusi- + -n = halusin (I wanted)
• tietää (Type 1) → tiesi- + -n = tiesin (I knew)
• tuntea (Type 1) → tunsi- + -n = tunsin (I felt/knew)

3. Vowel Changes
Adding -i- triggers specific changes to the stem's final vowel:

• -e, -i, -ä drop: lukea → luki, etsiä → etsi. Note: For Type 1 verbs ending in -ia/-iä (e.g., tanssia, oppia), the present and past forms are identical for most persons (e.g., minä tanssin = I dance / I danced). Context or the 3rd person singular form is needed to distinguish them.
• -a changes to -o: In 2-syllable verbs if the first vowel is a, e, or i (e.g., auttaa → auttoi).
• -a drops: In 2-syllable verbs if the first vowel is o or u (e.g., ostaa → osti), or in verbs with 3+ syllables.
• Long vowels and diphthongs: A long vowel shortens, whereas the diphthongs ie, uo, and yö lose their first vowel (e.g., saada → sai, juoda → joi). However, for verbs ending in a diphthong that ends in -i (e.g., voida, uida), the past tense -i- simply merges with the existing -i, resulting in no lost component (e.g., uida → uin).

4. Consonant Gradation
The imperfect follows consonant gradation rules, but the pattern depends on the verb type:

• Type 1: The 1st and 2nd persons (minä, sinä, me, te) use the weak grade, while the 3rd person (hän, he) uses the strong grade (e.g., minä luin vs. hän luki). Note that Type 1 verbs that change t to s (like tietää → tiesin) do not undergo consonant gradation in the past tense.
• Types 2 and 5: These generally do not undergo consonant gradation in the past tense, with the exception of the irregular Type 2 verbs tehdä → tein and nähdä → näin.
• Types 3, 4, and 6: These maintain the strong grade across all persons in the past tense (e.g., me tapasimme).

5. Negative Past Tense
To form the negative past, you do not use the -i- marker. Instead, use the negative verb followed by the past participle (e.g., minä en puhunut - I did not speak).

6. The 'Witnessed' Nuance
Finnish speakers often use the imperfect when they personally witnessed the event or know it as a definite fact. If they are only inferring that something happened, they might use the perfect tense instead.

Retained Vowels and an Irregular Stem
Stem-final o, ö, u, and y remain before past -i-: sanoa → sanoi and kysyä → kysyi. The verb käydä uses the special past stem käv-: minä kävin, hän kävi. Learn individual -taa/-tää verbs carefully: some have -ti-, some -si-, and some allow both; the surrounding consonants alone do not determine every verb.