| Quality Firstness | Brute Facts Secondness | Law Thirdness | |
| Sign | Qualisign: a sign made up of a quality, like the colour green | Sinsign: a sign made up of an existing physical reality, like a road sign on a street | Legisign: a sign made up of a law, like the sound of a referee's whistle in a game |
| Object | Icon: a sign relates to an object with some resemblance, like a photo | Index: a sign relates to the object in terms of causation, like a medical symptom | Symbol: the sign relates to the object by means of convention, like a word or a flag. |
| Interpretant | Rheme: a sign is represented for the interpretant as a possibility, like a concept | Dicent: a sign is represented for the interpretant as a fact, like a descriptive statement | Argument: the sign is represented for the interpreted as a reason, like a proposition. |