verb
to occur to (someone), to cave in / collapse
B1
Primary senses: 'to occur to someone / come to mind' and 'to cave in, collapse.' It's a separable strong verb (ein‑fallen) with stem vowel change (a→ä: du fällst, er fällt) and perfect 'eingefallen'. Uses auxiliary sein in perfect tenses. For 'occur' it takes a dative object (jemandem fällt etwas ein).
Examples
Dem Lehrer fiel plötzlich die Lösung ein, als die Schüler eine ähnliche Aufgabe lösten.
The teacher suddenly thought of the solution when the students solved a similar task.
Mir fiel bei der Prüfung nichts ein.
Nothing came to mind during the exam.
Ihm fiel der Name nicht ein.
He couldn't think of the name.
Details
Mnemonics
Picture an idea falling into a person's head (for 'occur to') and a roof falling inwards (for 'collapse').
Sounds like 'in-fall' — a thought falls into mind.
Notes
einfallen is separable: in main clauses the prefix 'ein' separates (er fällt mir ein). For the meaning 'to occur to someone' the person having the thought is typically in the dative (mir, dir, ihm...). For physical collapse meaning, the verb is used with sein in perfect tenses (ist eingefallen). | Intransitive verb; passive forms are not applicable.