The name of the civilisation
which informs and underlies many of Ursula K. LeGuin
's early books and short stories.
In the context of these books, Hain is the seed world of the human races. They use mind powers first developed on Rocannon's World and a Cetian mathematical notation.
The principle books of the Hainish Sequence are Rocannon's World, Planet of Exile, City of Illusions, The Left Hand of Darkness and The Dispossessed.
The Word for World is Forest (not originally published as a full novel) and a number of the stories in The Wind's Twelve Quarters are also Hainish. All of these works were published between the mid 1960s and mid 1970s. Le Guin has recently returned to this universe with The Telling and The Birthday of the World.