In relation to symbols or icons, the conceptual level is defined as the mental model of the viewer; semantic level is the meaning it conveys; syntactic level is attributed to its aesthetic quality or its arrangement on screen;
How would you describe the "lexical level" in connection to iconography?
Lexical level - related with vocabulary.
The lexical system has its internal structure. It consists of a network of formal, structural and functional dependencies occurring between individuals in the lexical system of a given language.
The icon itself is not a word but a visual image.
I think that the lexical dimension can strengthen the message and assure the user in the semantic / semantic dimension.
I recommend reading: