der Sender
station
A radio or television broadcasting organization that broadcasts programs.
Welcher Sender überträgt heute Abend das Fußballspiel?
Which station is broadcasting the football game tonight?

station / sender
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station
A radio or television broadcasting organization that broadcasts programs.
Welcher Sender überträgt heute Abend das Fußballspiel?
Which station is broadcasting the football game tonight?

'Der Sender' is derived from the verb 'senden' (to send). The ending '-er' refers to a person or thing that performs the action. A 'Sender' is therefore someone or something that sends something.
Dieser Radiosender spielt nur klassische Musik.
This radio station only plays classical music.
You can recognize the meaning of 'Sender' from the context. If it is about media such as radio or television, it refers to a broadcasting organization. If it is about mail or emails, it refers to the person who sends something. If it is about technology, it refers to a device.
Schalte bitte auf einen anderen Sender um.
Please switch to another station.
In the context of media, 'Sender' (station) is often used with verbs such as 'wechseln' (to change), 'einschalten' (to turn on), or 'umschalten' (to switch over). People also speak of 'private' (private) or 'öffentlich-rechtliche' (public-service) broadcasters.
Auf welchem Sender kommt die Nachrichtensendung?
Which station is the news program on?
radio
'das Radio' and 'der Sender' can both have to do with radio programs. 'Radio' often means the medium in general or what you hear. It can also refer to the institution. 'Sender' is more specific when it is about a particular radio or television broadcasting organization that broadcasts a program. Learners may confuse the words because in everyday speech people say 'Das läuft im Radio' (That's on the radio), but also 'Welcher Sender ist das?' (Which station is that?). For listening in general, 'Radio' is more natural; for the specific station, 'Sender' is more precise.

Der Sender bringt heute Abend ein Interview mit der Bürgermeisterin.
The station is airing an interview with the mayor this evening.
Im Auto läuft morgens meistens das Radio.
In the car, the radio is usually on in the morning.