Tugevadavad

Tugevadavad, commonly referred to as strong verbs, are a class of Estonian verbs distinguished from weak verbs by the way their past tense is formed. Rather than adding a uniform suffix to the stem, strong verbs typically change the stem vowel or consonant in the past tense, a phenomenon known as ablaut or stem alternation. This makes their across-form patterns more varied and, in some cases, less predictable.

In practice, strong verbs often show changes in the core of the verb when moving from present to past forms. Examples across Estonian include verbs such as nägema (to see) and tegema (to do), where the past forms nägin and tegin illustrate stem changes rather than simple suffixation. Another familiar pair is tulema (to come), whose past forms include tulin (I came) and tuli (he/she/it came) in different persons or tenses. Consonant gradation can accompany these vowel changes, further differentiating strong verbs from many weak verbs that rely on more regular suffix patterns.

Historically, the distinction between strong and weak verbs reflects developments in Proto-Finnic and the later Estonian language. Today, strong verbs constitute a smaller portion of the active vocabulary but remain important for correct past-tense formation and for understanding older texts. They are regularly taught in grammar descriptions and are encountered in both standard and dialectal usage, where the exact stem alternations may vary by verb and by spoken variety.

Overall, the category highlights a key area of Estonian morphology where internal stem changes carry the past tense, contrasting with the more suffix-driven endings of weak verbs.