complex and have changed over time, the three categories of signs that he distinguished stand out:

# The "icon," which relates to an object by resemblance to some quality of the object. A painted or photographed portrait is an icon by virtue of its resemblance to the painting's or photograph's subject. A more abstract representation, such as a map or diagram, can also be an icon.
# The "index," which relates to an object by some real connection. For