unbesetzt
unoccupied
Describes a place, seat, or room that is not currently being used by a person and is therefore free.
Entschuldigung, ist dieser Stuhl hier noch unbesetzt?
Excuse me, is this chair still unoccupied?

vacant / unoccupied
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unoccupied
Describes a place, seat, or room that is not currently being used by a person and is therefore free.
Entschuldigung, ist dieser Stuhl hier noch unbesetzt?
Excuse me, is this chair still unoccupied?

The word has a simple structure: the prefix 'un-' negates the adjective 'besetzt' (occupied/taken). 'besetzt' means 'taken' or 'occupied', so 'unbesetzt' literally means 'not occupied' or 'not taken'.
In der letzten Reihe waren noch einige Plätze unbesetzt.
There were still a few seats unoccupied in the last row.
The exact meaning of 'unbesetzt' (vacant/unoccupied) always depends on the noun it describes. An 'unbesetzter Stuhl' (unoccupied chair) is free, an 'unbesetzte Stelle' (vacant position) is an open job, and an 'unbesetzte Rolle' (uncast role) has not yet been assigned.
Die Firma sucht dringend einen neuen Mitarbeiter, da die Position seit Wochen unbesetzt ist.
The company is urgently looking for a new employee because the position has been vacant for weeks.
The adjective is often combined with the verb 'bleiben' (to remain) to express that a state continues. A seat, a position, or a role can 'unbesetzt bleiben' (remain vacant/unoccupied/uncast).
Es ist erstaunlich, dass diese wichtige Position so lange unbesetzt geblieben ist.
It is astonishing that this important position has remained vacant for so long.
In everyday life, the question 'Entschuldigung, ist hier noch unbesetzt?' (Excuse me, is this still free?) is a very common and polite way to ask whether a seat on public transport, in a café, or in a waiting room is available.
Der Mann zeigte auf den Stuhl neben mir und fragte: „Ist hier noch unbesetzt?“
The man pointed to the chair next to me and asked, 'Is this still free?'
free
'frei' and 'unbesetzt' can both mean that something is not yet being used by someone. 'frei' is more general and sounds very natural in everyday life, for example with a seat, table, or appointment. 'unbesetzt' sounds more precise when the point is that nobody is sitting in a seat, or that a job, position, or role has not yet been filled. In simple everyday situations, people often say 'frei'. In professional or official contexts, 'unbesetzt' is often a better fit.

Die Stelle im Sekretariat ist seit Montag unbesetzt.
The position in the secretary's office has been vacant since Monday.
Für Freitag ist noch ein Termin frei.
There is still an appointment available for Friday.