publisher; publishing house; publishing company
Refers to a company or organization that publishes books, magazines, etc.
He works for a major publishing company.
That publisher released a new novel.
He brought his manuscript to a major publisher.
That book was published by a famous publisher.
She works as an editor at a publishing company.
He applied for a job at a major publisher.
出版社 is the standard modern term for a publishing company, whereas 書房 is a more literary or traditional way to refer to one, often used in its actual name.