More precise categorisation: past-participle adjective.
The returned book was placed back on the shelf.
Возвращённая книга была поставлена обратно на полку.
The returned soldier was welcomed by his family.
Вернувшийся солдат был встречен своей семьёй.
Plural-only noun: ‘people who have come back’, especially after war, migration, or exile.