A Sinsign (where the syllable sin is taken as meaning “being only once,” as in single, simple, Latin semel, etc.) is an actual existent thing or event which is a sign. It can only be so through its qualities; so that it involves a qualisign, or rather, several qualisigns. But these qualisigns are of a peculiar kind and only form a sign through being actually embodied.
…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.
…in the first place a sign may, in its own firstness, either be a mere idea or quality of feeling, or it may be a ‘sinsign’, that is, an individual existent (and P. holds, with Hegel, that existence consists in the blind reaction of the existent with the rest of the universe in which it exists), or it may (like a word) be a general type (‘legisign’) to which existents may conform.
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 sinsign is a definite individual existent which is significant because of the circumstances of its existence, which are either significant or include the very object denoted.