From Proto-Finnic *teetädäk, probably derived from Proto-Finnic *tee (“road, way”) (modern Estonian tee). In this case the verb seems to have originally meant ’to know the way’. Cognates include Võro tiidmä, Livonian tied, Votic täätä; Finnish tietää, Ingrian tiitää, Livvi tiediä, Ludian tieta, Veps teta.
The standard language stem tead- originates from dialects, where the long vowel has diphthongized, which results in this word instead of the expected *teedma. Alternatively, the strong grade stem results from analogy with verb forms formed from weak grade (mostly present tense, *teedät > *teeat > tead "you know").
teadma (da-infinitive teada)
| indicative | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| present | perfect | ||||||||
| person | positive | negative | person | positive | negative | ||||
| 1st sing. | tean | ei tea | 1st sing. | olen teadnud | ei ole teadnud pole teadnud | ||||
| 2nd sing. | tead | 2nd sing. | oled teadnud | ||||||
| 3rd sing. | teab | 3rd sing. | on teadnud | ||||||
| 1st plur. | teame | 1st plur. | oleme teadnud | ||||||
| 2nd plur. | teate | 2nd plur. | olete teadnud | ||||||
| 3rd plur. | teavad | 3rd plur. | on teadnud | ||||||
| impersonal | teatakse | ei teata | impersonal | on teatud | ei ole teatud pole teatud | ||||
| past | pluperfect | ||||||||
| person | positive | negative | person | positive | negative | ||||
| 1st sing. | teadsin | ei teadnud | 1st sing. | olin teadnud | ei olnud teadnud polnud teadnud | ||||
| 2nd sing. | teadsid | 2nd sing. | olid teadnud | ||||||
| 3rd sing. | teadis | 3rd sing. | oli teadnud | ||||||
| 1st plur. | teadsime | 1st plur. | olime teadnud | ||||||
| 2nd plur. | teadsite | 2nd plur. | olite teadnud | ||||||
| 3rd plur. | teadsid | 3rd plur. | oli teadnud | ||||||
| impersonal | teati | ei teatud | impersonal | oli teatud | ei olnud teatud polnud teatud | ||||
| conditional | |||||||||
| present | perfect | ||||||||
| person | positive | negative | person | positive | negative | ||||
| 1st sing. | teaksin | ei teaks | 1st sing. | teadnuksin oleksin teadnud |
ei teadnuks ei oleks teadnud poleks teadnud | ||||
| 2nd sing. | teaksid | 2nd sing. | teadnuksid oleksid teadnud | ||||||
| 3rd sing. | teaks | 3rd sing. | teadnuks oleks teadnud | ||||||
| 1st plur. | teaksime | 1st plur. | teadnuksime oleksime teadnud | ||||||
| 2nd plur. | teaksite | 2nd plur. | teadnuksite oleksite teadnud | ||||||
| 3rd plur. | teaksid | 3rd plur. | teadnuksid oleksid teadnud | ||||||
| impersonal | teataks | ei teataks | impersonal | oleks teatud | ei oleks teatud poleks teatud | ||||
| imperative | |||||||||
| present | perfect | ||||||||
| person | positive | negative | person | positive | negative | ||||
| 1st sing. | — | — | 1st sing. | — | — | ||||
| 2nd sing. | tea | ära tea | 2nd sing. | ole teadnud | ära ole teadnud | ||||
| 3rd sing. | teadku | ärgu teadku | 3rd sing. | olgu teadnud | ärgu olgu teadnud | ||||
| 1st plur. | teadkem | ärme teame ärme tea ärgem teadkem |
1st plur. | olgem teadnud | ärme oleme teadnud ärme ole teadnud ärgem olgem teadnud | ||||
| 2nd plur. | teadke | ärge teadke | 2nd plur. | olge teadnud | ärge olge teadnud | ||||
| 3rd plur. | teadku | ärgu teadku | 3rd plur. | olgu teadnud | ärgu olgu teadnud | ||||
| impersonal | teatagu | ärgu teatagu | impersonal | olgu teatud | ärgu olgu teatud | ||||
| quotative | |||||||||
| present | perfect | ||||||||
| voice | positive | negative | voice | positive | negative | ||||
| active | teadvat | ei teadvat | active | olevat teadnud | ei olevat teadnud polevat teadnud | ||||
| passive | teatavat | ei teatavat | passive | olevat teatud | ei olevat teatud polevat teatud | ||||
| Nominal forms | |||||||||
| ma-infinitive | active | passive | da-infinitive | present | past | ||||
| nominative | teadma | teatama | nominative | teada | olla teadnud | ||||
| illative | — | inessive | teades | olles teadnud | |||||
| inessive | teadmas | participle | active | passive | |||||
| elative | teadmast | present | teadev | teatav | |||||
| translative | teadmaks | past | teadnud | teatud | |||||
| abessive | teadmata | negative | teadmatu | — | |||||