Phatic - Denoting speech used to create an atmosphere of goodwill.
Susan Bones didn't really like Hermione Granger when they first met. The girl was too bossy, too fond of imparting the knowledge she'd gleaned from those precious books of hers. But, knowing it had to be hard for the Muggle-born, who'd never known of this world before, to adjust, she let her walk into the Great Hall alongside her, chattering excitedly about how the Great Hall's ceiling was bewitched to look like the sky outside.
Unknown to Susan, the Sorting Hat saw her. He noted her kindness. He noted it and realised that she would have to be a Hufflepuff.