1. A room to dine in.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• diningroom,
• dinningroom,
• sining-room,
• xining-room,
• cining-room,
• fining-room,
• rining-room,
• eining-room,
• duning-room,
• djning-room,
• dkning-room,
• doning-room,
• d9ning-room,
• d8ning-room,
• dibing-room,
• diming-room,
• dijing-room,
• dihing-room,
• dinung-room,
• dinjng-room

The adjective form of "dining-room" is "dining-room". It is used to describe or modify nouns, as in phrases like "a cozy dining-room" or "a spacious dining-room".

The plural form of "dining-room" is "dining-rooms".

The singular form of "dining-room" is "dining-room". The word does not change when expressing it in the singular form.