reserved

adjective

Pronunciation: /ɹɪˈzɝvd/ / /ɹɪˈzɜːvd/

Slow to reveal emotion or opinions.
“He was a quiet, reserved person.”
“Before I met Mr. Bowen Cooke I had been given to understand that he was of a reserved nature, and on occasion could be a "bit of a martinet"; [...].”
Set aside for a particular person or purpose; spoken for.
“Near-synonyms: allocated, assigned, dedicated”
“I'm sorry, sir, but these are reserved seats.”