Breakdown of Sei bitte vernünftig und fahr langsamer.
und
and
fahren
to drive, to travel
langsam
slow, slowly
bitte
please
vernünftig
reasonable, sensible
Questions & Answers about Sei bitte vernünftig und fahr langsamer.
Why is there no umlaut in fahr? I learned that fahren becomes du fährst.
In the informal singular (du) imperative, strong verbs that change their vowel from a to ä in the present tense drop the umlaut. So fahren becomes fahr (or fahre), never fähr. By contrast, verbs that change from e to i or ie do keep their vowel change in the imperative, like lesen becoming lies.
Is sei an exception for the imperative?
Yes, the verb sein is highly irregular. Its imperative forms don't derive neatly from a present tense stem. The du form is sei, the ihr form is seid, and the formal Sie form is seien Sie.
Could I use sinnvoll instead of vernünftig to mean "sensible" here?
Not really. English often uses "sensible" for both, but German distinguishes them. Vernünftig relates to human reason and is used for people and their behavior (acting reasonably). Sinnvoll means "making sense" or "useful" and applies to ideas, rules, or plans. Since you are asking a person to behave reasonably, vernünftig is the right choice.
Is the -er on langsamer an adjective declension ending?
No, it is the comparative form of the adverb langsam (slow). Unlike English, which usually adds "more" to make an adverb comparative ("more slowly"), German simply adds -er to the base word for both adjectives and adverbs.
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