adverb
on
A1
An (adverb) commonly means 'on' in two senses: 1) at or touching a surface (e.g. an der Wand), 2) switched on/operational (e.g. Licht an). Specialties: it's an adverb/particle, not a full preposition; often appears in separable verbs like anmachen. colloquially.
Examples
Der Mann klopfte an, während die Familie drinnen schlief.
The man knocked while the family slept inside.
Das Licht ist an.
The light is on.
Details
Mnemonics
a light switch labeled 'AN' (on) glowing
like English 'on' — very short
Notes
'an' as an adverb often indicates a state (e.g., a device is on). Different from the preposition 'an' though identical in form.