Semeiotic is a term meaning the way Charles S. Peirce often pronounced the word meaning the general science of signs. Therefore, it is synonymous with the more commonly used and more widely accepted semiotics.
Sometimes the semeiotic is used to separate Peirce’s or his followers’ approach to the study of signs from other approaches (for example, that of Ferdinand de Saussure).
For the same reason, semiology is sometimes used to distinguish the orientation of Saussure and his followers from other orientations.
Some semioticians tend to over-read the signs into something that is, essentially not true. Therefore, we are to share with you that, the name of the website – semiology.net is not in any manner an attempt to demonstrate affiliation, nor preference towards Saussure’s understanding of the signs. The reason is trivial, and one could say pragmatic – that was the only available reasonable domain name.