das Rotlicht
red light
The red light of a traffic signal, which tells vehicles and pedestrians that they must stop.
Er hat das Rotlicht übersehen und einen Unfall verursacht.
He missed the red light and caused an accident.

red light
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red light
The red light of a traffic signal, which tells vehicles and pedestrians that they must stop.
Er hat das Rotlicht übersehen und einen Unfall verursacht.
He missed the red light and caused an accident.

The word is a simple compound made from the adjective 'rot' (red) and the noun 'Licht' (light). This literal meaning is the basis for all specific uses.
Das rote Licht der untergehenden Sonne tauchte die Landschaft in warme Farben.
The red light of the setting sun bathed the landscape in warm colors.
Since the word has very different meanings, context is crucial. Words like 'Ampel' (traffic light) or 'Straße' (street) point to the traffic meaning (m01), 'Milieu' (milieu) or 'Viertel' (district) to prostitution (m02), and 'Lampe' (lamp) or 'Wärme' (heat) to the therapeutic use (m03).
Fahren Sie bitte erst bei Grün, das Rotlicht ist noch an.
Please only drive when the light is green; the red light is still on.
In a traffic context, there are fixed expressions. You can 'ein Rotlicht überfahren' (run a red light) or 'missachten' (disregard it), and you must stop 'bei Rotlicht' (at a red light).
Wer ein Rotlicht überfährt, muss mit einer hohen Strafe rechnen.
Anyone who runs a red light must expect a heavy fine.
In the meaning 'Prostitution' (prostitution), 'Rotlicht' (red light) is often used as part of compound nouns, for example 'das Rotlichtmilieu' (the red-light milieu), 'das Rotlichtviertel' (the red-light district), or 'die Rotlichtszene' (the red-light scene).
Der Journalist recherchiert für eine Reportage über das Rotlichtmilieu der Stadt.
The journalist is doing research for a report on the city's red-light milieu.
prostitution
'die Prostitution' and 'das Rotlicht' can both have to do with sexual services in exchange for money. 'Prostitution' is the direct and factual term for this activity or trade. In this context, 'Rotlicht' refers more to the environment or milieu, for example streets, bars, or businesses connected with it. The words can be confused because 'Rotlicht' is often used as a short way to refer to this area. If you are speaking precisely about the activity, 'Prostitution' is clearer. If you are talking about the milieu or an area, 'Rotlicht' is more appropriate.

In dieser Straße gibt es viele Bars, deshalb spricht man dort oft vom Rotlicht.
There are many bars on this street, so people there often talk about the red-light district.
In der Diskussion ging es um die Rechte von Menschen in der Prostitution.
The discussion was about the rights of people in prostitution.