Silk Chiffon
A sheer, lightweight, plain-weave silk fabric with a slightly rough hand, prone to fraying.
Chiffon is woven from tightly twisted crepe yarns in alternating directions, which is what gives it that slightly rough, almost gritty hand and the springy, slightly puckered drape — it's sheer but it isn't limp the way some sheers are. Beautiful for overlays, sleeves, and anything that needs to move.
Honestly, this is the fabric I have the most complicated relationship with. It's gorgeous to wear and miserable to sew: it slips on the cutting table, frays if you so much as glare at a raw edge, and a domestic machine's feed dogs will happily eat the leading edge of it if you're not careful. I always cut it on a layer of tissue paper (cut through both, tear the tissue away after), and every seam gets a French seam or a narrow rolled hem — nothing raw is ever left exposed, because it will unravel.
Worth it for the right project. Just budget more time than you think you need, and don't attempt your first chiffon garment the week before you need to wear it.