Ferdinand de Saussure's theory of the signifier and signified, when applied to the literary vampire, helps us explain the phenomenon of the modern vampire. Culturally, we all have an internalised image of a vampire; mine is Christopher Lee, yours maybe Tom Cruise, but we all have one or an amalgamation of many. The word is universal; it has to be and it is the signifier our internal image, the signified, giving meaning to the word.
This is a simplistic explanation: A signifier in linguistics is the marks (letters) we string together to make a unique word. Take the word tree; when you see this word in text, t-r-e-e has no actual link with the natural world. As we read, we see the letters and interpret them, fitting them to our internal, mental image of a tree. As children we absorb our verbal language from the world around us. Sounds become words and words become sentences as we gradually learn how to communicate with the world around us. Our brains are like sponges; as small children, up to the age of 11, we have a capability to learn language that fades as we get older. Before we ever learn about the signifier, we have already learnt what is signified by the words for the things we experience all around us. To reinforce the link, most books for very small children have both the word and a picture, so that the link is instant in the child's mind.
So, back to the vampire. When we see this word, we all have an internal image, as I've said before. What is strange about the vampire in modern literature is that this image is fluid. What do I mean by fluid? Compare two vampires Dracula and Lestat. What is it they share that makes them 'vampires'? They are both evil, that isn't true. They both drink blood, true. They are both nocturnal, not true. They kill indiscriminately, isn't true. They both have pointy teeth, true. So, the only two characteristics Dracula and Lestat share in the above list is that they both drink blood and both have pointy teeth. Both characters are vampires, the only thing that separates them is the century they were written in. In the last millennium, the signified for the vampire was different than it is today, the vampire was the signifier for evil and the corruption of good by ancient bloodlines. After the French and Russian revolutions, unrest raged throughout Europe and the vampire, with his noble, but corrupt blood, is the signified for the old order, the hated royalty and debauched landed gentry who bled the peasants dry.
Today's vampire is both evil, villain, saviour and hero. Writers of vampire fiction in this millennium are painting their image of a vampire with a much fuller pallet. The reader's relationship with the vampire has changed beyond anything Bram Stoker could have foretold when he transported Dracula from folklore into a new technological age. The old world met the new in Dracula and the new age, a time of science and invention won or did it?