Another aspect of semiotics is Syntagm and paradigm, below is what each are them are:
Syntagm: A single word or element of design that; when altered can change the overall meaning.
Paradigm: A group or related ideas that are interchangeable in a sentence or design, yet they still have the same collective meaning.
The best way for me to show this theory is to design it, I did this quickly on illustrator but it shows this the best way, so the sentence is clear and simple it allows the reader to envision what is begin said which is a Paradigm, but when a Syntagm is changed it changes the sentence completely and as designers this is important, a cat sitting on a mat is one thing but change the mat to a wall, it’s completely different.
Another Image showing this aspect of semiotics in great detail: