If there's more emotion, more movement (and chances are, if the figure is reclining) it's a Hellenistic sculpture. The oldest pieces have impassive nude figures simply stepping forward slightly, called kouros. Classical sculptures have the perfect dimensions and the ethereal, beatific air about them, and are often free-standing sculptures as well, except in more interesting positions; instead of merely stepping forward, they're perhaps leanding casually on a column, or maybe in mid-spin of throwing a dicsus.