verb
to arrest, to take into custody
B1
Festnehmen: separable verb meaning 'to arrest' or 'to take into custody'. Transitive, non-reflexive; auxiliary haben. Irregular strong verb: stem change present e->i (du nimmst fest, er nimmt fest), preterite nahm fest, participle festgenommen. Imperative irregular: Nimm fest! / Nehmen Sie fest!
Examples
Der Täter wurde von der Polizei festgenommen.
The perpetrator was arrested by the police.
Die Polizei hat den Verdächtigen gestern festgenommen.
The police arrested the suspect yesterday.
Er wurde wegen Verdachts der Diebstahls festgenommen und zur Wache gebracht.
He was taken into custody on suspicion of theft and brought to the station.
Details
Mnemonics
Picture police officers literally 'taking someone fast' and holding them (taking into custody)
sounds like 'fast' + 'name' (fast-name = grab a name)
Notes
Separable verb with irregular stem (nehmen): present tense shows vowel change (du nimmst, er nimmt); past forms use ‚nahm‘ and participle is 'festgenommen'. Used in legal/police contexts.