1. "Semiotics is the study of the role of signs in human life." F. Saussure
2. "Semiotics is concerned with everything that can be taken as a sign." Umberto Eco
3. "Semiology aims to take in any system of signs, whatever their substance and limits; images, gestures, musical sounds, objects, and the complex associations of all of these, which form the content of ritual, convention or public entertainment: these constitute, if not languages, at least systems of signification." Roland Barthes 

sign - sign(nificant)

Semiotic is related to linguistics, or part of it or vice versa:
semantics: the relationship of signs to what they stand for 
syntactics (or syntax): the formal or structural relations between signs
pragmatics: the relation of signs to interpreters 

Saussure saw linguistics as a branch of 'semiology': 
"Linguistics is only one branch of this general science [of semiology]. The laws which semiology will discover will be laws applicable in linguistics... As far as we are concerned... the linguistic problem is first and foremost semiological... If one wishes to discover the true nature of language systems, one must first consider what they have in common with all other systems of the same kind... In this way, light will be thrown not only upon the linguistic problem. By considering rites, customs etc. as signs, it will be possible, we believe, to see them in a new perspective. The need will be felt to consider them as semiological phenomena and to explain them in terms of the laws of semiology." (Saussure 1983, 16-17; Saussure 1974, 16-17)

In the first place is the expression. Expression configures itself into a system of signs that include gestures, sounds, movements, constructions etc. Visually these find order in the world of symbols. As sound they evolve into systems of languages (speech or music). As signs they evolve into script. In three dimension the evolve into architecture.
On all levels they find their highest expression in ART. What we percieve as 'reality' is in fact no more than a system of 'signs' - semionics.
One could say that art a refined form of semiology. )(SFM)

Semiology expresses itself via 'semiosis'. This is the ongoing process by which culture produces signs and gives meaning to them. This is a social activity modified my subjective factors. Each individual may provide subjective interpretation of signs. 

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References:
Semiotics for Beginners - David Chandler