der Sitzplatz
seat
An assigned or available place intended for sitting, for example in a vehicle, cinema, or stadium.
Im Zug war leider kein freier Sitzplatz mehr verfügbar.
Unfortunately, there was no free seat available on the train anymore.

seat
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seat
An assigned or available place intended for sitting, for example in a vehicle, cinema, or stadium.
Im Zug war leider kein freier Sitzplatz mehr verfügbar.
Unfortunately, there was no free seat available on the train anymore.

The word 'Sitzplatz' (seat) is made up of 'Sitz' (from the verb 'sitzen' — to sit) and 'Platz' (place/space). So it literally means a 'place to sit'.
Gibt es in diesem Abteil noch einen freien Sitzplatz am Fenster?
Is there still a free window seat in this compartment?
Common verbs used with 'Sitzplatz' (seat) are 'einen Sitzplatz reservieren' (to reserve a seat), 'buchen' (to book), 'suchen' (to look for), or 'finden' (to find).
Für die lange Zugfahrt sollten Sie unbedingt einen Sitzplatz reservieren.
For the long train journey, you should definitely reserve a seat.
A common instruction on public transportation or at events is 'Bitte nehmen Sie Ihre Sitzplätze ein' (please take your seats). This means that you should sit down.
Bitte nehmen Sie Ihre Sitzplätze ein, die Vorstellung beginnt in wenigen Minuten.
Please take your seats; the performance will begin in a few minutes.
place / space
'der Platz' and 'der Sitzplatz' can both mean a place where a person can sit. 'Platz' is more general: it can be a seat, a free spot, or simply available space. 'Sitzplatz' is more precise and clearly says that you are supposed to sit there or can sit there, for example on a train, in a cinema, or in a stadium. The words can easily be confused because in everyday language people often simply say 'Platz' even when they mean a seat. When sitting is important, 'Sitzplatz' is more precise.

Im Zug habe ich einen Sitzplatz am Fenster reserviert.
I reserved a window seat on the train.
Ist neben dir noch ein Platz frei?
Is there still a seat free next to you?