In an earlier post, I outlined how German auxiliaries and the various verb principal parts work together in forming each of the verb tenses. There I listed some representative verbs to show the patterns that exist in the formation of the principal parts. Principal parts are the basic forms of a verb a speaker must know in order to form all possible tenses. Here I’d like to look more closely at those patterns.
There are three categories of verbs in German based on how they form their principal parts: weak verbs, strong verbs, and mixed verbs. It is impossible to identify what category a verb belongs to just by looking at its infinitive. The forms of the simple past stem and past participle, on the other hand, make evident which category a verb belongs to (with just a few exceptions).
Strong verbs and most mixed verbs have at least one principal part with a stem change. The simple past tense of all strong and most mixed verbs involves a stem change. Many of them also have stem changes in their past participle. And some even have anomalies in their present tense conjugations.
Principle parts pattern for strong verbs:
[verb stem](e)n, [changed verb stem], ge[changed? verb stem](e)n
rufen, rief, gerufen
bleiben, blieb, geblieben
ziehen, zog, gezogen
tun, tat, getan
A small group of strong verbs also has a stem change in present tense du- and er-forms.
fahren (du fährst/er fährt), fuhr, gefahren
essen (du isst/er isst), aß, gegessen
Principle parts pattern for mixed verbs:
[verb stem](e)n, [changed? verb stem]te, ge[changed? verb stem]t
nennen, nannte, genannt
bringen, brachte, gebracht
denken, dachte, gedacht
Some mixed verbs also have anomalies in their present tense singular conjugations.
wissen (ich weiß/du weißt/er weiß), wusste, gewusst
dürfen (ich darf/du darfst/er darf), durfte, gedurft
haben (du hast/er hat), hatte, gehabt
Weak verbs have principal parts that can be predictably derived from the infinitive and they follow a predictable pattern of conjugation in every verb tense. So the only form of a weak verb you need to memorize is the infinitive. Here are the principal parts of some weak verbs for the sake of comparison with the strong/mixed verb patterns above.
Principle parts pattern for weak verbs:
[verb stem](e)n, [verb stem]te, ge[verb stem](e)t
fehlen, fehlte, gefehlt
sagen, sagte, gesagt
spielen, spielte, gespielt
reden, redete, geredet
handeln, handelte, gehandelt
In the end, what is important to know is that the forms of strong and mixed verbs must be committed to memory so that you can recognize and use them when the need arises. So as you learn new verbs, take note of any stem changes and learn the principal parts of any verb that is strong or mixed. While it may seem a daunting task at first, the list of these verbs is finite and the most common stems are used repeatedly in derived words (e.g. bieten, bot, geboten / anbieten, bot an, angeboten > noun: Angebot / verbieten, verbot, verboten > noun: Verbot). For this reason, knowing the basic stem changes also has the added benefit in aiding vocabulary expansion.