Semeion is a Greek word for sign.
Long ago (starting with Hippocrates and Parmenides in the 5th century BC) semeion was used as a synonym for tekmerion (clue, proof, symptom).
In the writings of some ancient Greek authors (for example, in many of Aristotle‘s texts), semeia differs from symbola. The semeion paradigm was a medical symptom (e.g., spots); the symbolum paradigm, on the other hand, was a linguistic expression.
There is an internal or natural connection between a semeion (sign) and what it means, on the contrary, there is only a random or conventional connection between a symbol and what it symbolizes.
But as in modern English, the gap between sign and symbol in ancient Greek usage has not been drawn consistently and clearly.
