How did Charles Sanders Peirce classify signs as icons, indexes, and symbols?

Charles Sanders Peirce, a foundational figure in semiotics, defined a sign as "something which stands to somebody for something." Within his broader logical framework, he categorized signs into three primary types based on their relationship to their referents:12

• Icon: A sign that represents its referent through resemblance or similarity, such as a road sign depicting falling rocks.1
• Index: A sign that is directly associated with or connected to its referent, such as smoke serving as a sign of fire.1
• Symbol: A sign that relates to its referent solely through convention, law, or habit, such as words or traffic signals.1

Peirce viewed these categories as part of a systematic approach to logic, which he identified as the general theory of signs. He emphasized that signs do not possess a fixed, static meaning; rather, their significance is continuously qualified through the process of semiosis.12