der Passant
passerby
A person who happens to pass by a place, usually on foot on a street or square.
Ein Passant fand die verlorene Brieftasche auf dem Gehweg.
A passerby found the lost wallet on the sidewalk.

passerby
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passerby
A person who happens to pass by a place, usually on foot on a street or square.
Ein Passant fand die verlorene Brieftasche auf dem Gehweg.
A passerby found the lost wallet on the sidewalk.

'Der Passant' (the passerby) belongs to the N-declension. This means that it takes the ending '-en' in all cases except the nominative singular. This also applies to the plural.
Die Polizei befragte den Passanten als Zeugen.
The police questioned the passerby as a witness.
The word 'Passant' (passerby) is closely related to the verb 'passieren', which means 'to pass by' or 'to happen'. A Passant is therefore literally a person who passes by a place.
Viele Passanten blieben stehen, um dem Straßenmusiker zuzuhören.
Many passersby stopped to listen to the street musician.
The word is often used in reports about accidents or events in public spaces. A typical combination is 'ein zufälliger Passant' (a random passerby).
Ein aufmerksamer Passant rief die Feuerwehr.
An attentive passerby called the fire department.
visitor
'der Besucher' and 'der Passant' can both be people at a place, but they do not have the same role there. A visitor comes to a place with a purpose, for example to a shop, a museum, an event, or to someone’s home. A passerby is just passing by by chance, usually on the street or in a square. The words can be confused when there are many people in one place. The important point is the intention: someone who goes in or visits something is a 'Besucher'; someone who is only passing by is a 'Passant'.

Ein Passant bleibt kurz stehen, weil er die laute Musik auf dem Platz hört.
A passerby stops briefly because he hears the loud music in the square.
Wegen der neuen Ausstellung kommen am Wochenende besonders viele Besucher ins Museum.
Because of the new exhibition, especially many visitors are coming to the museum this weekend.