The word ‘dinner’ is a noun. It refers to a meal, typically the main meal of the day, which is usually eaten in the evening. In conversations and writing, nouns serve as the names of people, places, things, or ideas. Since ‘dinner’ falls into the category of a thing—specifically a meal—it is classified as a noun.
For example, in the sentence, ‘We are having dinner at 7 PM,’ the word ‘dinner’ names the meal being eaten, clearly demonstrating its role as a noun.