What physically makes a hat? The true definition is a headpiece that has a crown and a brim. Round crowns, flat crowns, square crowns, crowns that slope on one side, everyone giving a  different look to the hat. Brims, there are endless designs. Small, large, up turn down turn, up turn and down turn all in one brim. It all depends on your height, build and shape of face that will determine which you choose. Be adventurous!!!!