die Lobby
lobby
The large entrance hall in a hotel, theater, or another public building.
Wir können uns um acht Uhr in der Lobby des Kinos treffen.
We can meet at eight o'clock in the lobby of the movie theater.

lobby
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lobby
The large entrance hall in a hotel, theater, or another public building.
Wir können uns um acht Uhr in der Lobby des Kinos treffen.
We can meet at eight o'clock in the lobby of the movie theater.

The meaning of 'Lobby' (lobby) is almost always clear from context. If people are talking about a building (hotel, theater), it means the entrance hall. In a political or economic context, it means an interest group.
Warten Sie bitte einen Moment in der Lobby, der Manager kommt gleich.
Please wait a moment in the lobby; the manager will be here shortly.
When you are in the entrance hall or are going there, the preposition 'in' is used. Being there is expressed with the dative ('in der Lobby' — in the lobby), movement toward it with the accusative ('in die Lobby' — into the lobby).
Ich habe eine Stunde in der Lobby auf dich gewartet.
I waited for you in the lobby for an hour.
In the political sense, 'Lobby' (lobby) is often used as the second part of a compound to name the respective interest group. Examples are 'Agrar-Lobby' (agricultural lobby), 'Pharma-Lobby' (pharmaceutical lobby), or 'Auto-Lobby' (auto lobby).
Die Auto-Lobby hat großen Einfluss auf die Verkehrspolitik.
The auto lobby has a major influence on transport policy.
When referring to interest groups, 'Lobby' (lobby) is often combined with verbs such as 'Einfluss nehmen/ausüben' (to exert influence), 'Interessen vertreten' (to represent interests), or 'Druck machen' (to apply pressure).
Die Organisation versucht, als Lobby auf die Regierung Einfluss zu nehmen.
The organization is trying to exert influence on the government as a lobby.
hall
'die Halle' and 'die Lobby' can both mean the large entrance area of a public building. 'Lobby' is used especially often for hotels, theaters, or modern buildings where people wait or meet. 'Halle' is more general and can also mean other large rooms, for example a sports hall or warehouse hall. Learners may confuse the words when talking about the entrance of a building. As a simple guide: in a hotel, 'Lobby' sounds very natural; for a large room in general, 'Halle' fits better.

Anna hat nach dem Gespräch in der Lobby des Hotels auf ein Taxi gewartet.
After the meeting, Anna waited for a taxi in the hotel lobby.
Nach dem Konzert warteten viele Besucher in der Halle auf ihre Freunde.
After the concert, many visitors waited in the lobby for their friends.