How do you spell Inanity

Available Definitions:
1)  n. - Inanition; void space; vacuity; emptiness.
2)  n. - Want of seriousness; aimlessness; frivolity.
3)  n. - An inane, useless thing or pursuit; a vanity; a silly object; -- chiefly in pl.; as, the inanities of the world.