
versehentlich
accidentally
By mistake, without intention, or happening unintentionally.
Ich habe dir versehentlich die falsche Datei geschickt.
I accidentally sent you the wrong file.
accidentally
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accidentally
By mistake, without intention, or happening unintentionally.
Ich habe dir versehentlich die falsche Datei geschickt.
I accidentally sent you the wrong file.
'Versehentlich' (accidentally) is derived from the noun 'das Versehen' (mistake or error). The ending '-lich' turns it into an adverb that describes how an action happens.
Das war ein Versehen, es tut mir leid.
That was a mistake; I'm sorry.
As an adverb, 'versehentlich' (accidentally) can stand flexibly in the sentence. It often appears directly before the part it modifies, or at the beginning of the sentence for emphasis (then the verb follows in position 2).
Er hat die E-Mail versehentlich gelöscht.
He accidentally deleted the email.
'Versehentlich' (accidentally) is often combined with everyday mistakes, especially in the digital realm. Typical phrases are: 'versehentlich löschen' (to accidentally delete), 'versehentlich anrufen' (to accidentally call), or 'versehentlich etwas Falsches bestellen' (to accidentally order the wrong thing).
Ich habe dich gestern Abend versehentlich angerufen, als mein Handy in der Tasche war.
I accidentally called you last night when my phone was in my bag.
random / by chance
Zufällig and versehentlich both describe something unplanned. Zufällig emphasizes that the course of events was determined by chance; versehentlich identifies an unintended action as a mistake. Use zufällig for a random selection and versehentlich for a mistake.

Ich nahm versehentlich den falschen Schlüssel aus der Schublade.
I accidentally took the wrong key from the drawer.
Ich nahm zufällig den ersten Schlüssel aus der Schublade.
I picked the first key from the drawer at random.