The chlamys was a type of an ancient Greek cloak. By the time of the Byzantine Empire it was, although in a much larger form, part of the state costume of the emperor and high officials. It survived as such until at least the 12th century AD.
Hermes wearing a chlamys
King David in the Paris Psalter, 10th century AD
A chlamys-wearing torso, possibly of Alexander
Ptolemy III as Hermes wearing the chlamys
A cloak is a type of loose garment worn over clothing, mostly but not always as outerwear for outdoor wear, serving the same purpose as an overcoat, protecting the wearer from the weather. It may form part of a uniform. People in many different societies may wear cloaks. Over time cloak designs have changed to match fashion and available textiles.
A young man in an evening cloak, 1823.
Cloak, 1580–1600 Victoria and Albert Museum, No. 793-1901
Couple hiding under the same cloak, fragment of an Ancient Greek red-figure cup, ca. 525 BC–500 BC, found in Athens. Louvre Museum, Paris.