A Qualisign is a quality which is a Sign. It cannot actually act as a sign until it is embodied; but the embodiment has nothing to do with its character as a sign.
… a Qualisign is any quality in so far as it is a sign. Since a quality is whatever it is positively in itself, a quality can only denote an object by virtue of some common ingredient or similarity; so that a Qualisign is necessarily an Icon. Further, since a quality is a mere logical possibility, it can only be interpreted as a sign of essence, that is, as a Rheme.
…signs are divisible, first, according to their modes of being, as objects; secondly, according to the modes of their references to their objects; thirdly, according to the modes of their references to their interpretants. In the first way of dividing them, signs are either qualisigns, or signs that are abstract qualities (in a wide sense), or suisigns, signs that are essentially existent as individual objects or events, or legisigns, signs that [are] general types, laws, or habits.
As it is in itself, a sign is either of the nature of an appearance, when I call it a qualisign; or secondly, it is an individual object or event, when I call it a sinsign (the syllable sin being the first sillable [sic] of semel, simul, singular, etc); or thirdly, it is of the nature of a general type, when I call it a legisign.
The qualisign […] has no identity. It is the mere quality of an appearance & is not exactly the same throughout a second. Instead of identity, it has great similarity, & cannot differ much without being called quite another qualisign.
A sign in itself may be an indefinite possibility, when I term as a Qualisign, or it may be an existent thing or event, when I term it a Sinsign (sin- is the sim- of simul, simplex, etc.), or it may be a general type, when I call it a Legisign.
Parenthetical comment enclosed in square brackets in the original manuscript
A qualisign is an aspect, impression, or other priman significant regardless of its parts or of anything else simply because it involves the very character signified.