I'm very confused if I should use "the ghost" or "ghosts" or "a ghost" It's 'a ghost', if it is one ghost, but not a specific or particular ghost. It's 'the ghost', if it is one ghost, but a specific or particular one, or one you were just talking about It's 'ghosts', if it is more than one ghost, but you are not talking about any particular or specific group of ghosts, you are just referencing ghosts in general. It's 'the ghosts', if it is more than one ghost, AND a particular group, or ghosts you were just talking about. Using some of your examples: B: Why are you blaming a ghost? (or ghosts?) You are not specifying a particular ghost, so for plural you would say: Why are you blaming ghosts ? A: I don’t think it’s the ghost. (or the ghosts?) Have you ever seen him like this before? You are talking about a particular ghost, so plural would be: I don’t think it’s the ghosts. Have you ever seen him like this before?