Which field studies the use of orthographic signs within a writing system?

Graphemics is the field that focuses on the study of graphemes, which are the smallest functional units of writing within a writing system. It examines how these orthographic signs, including letters, punctuation marks, and other symbols, are organized to represent language in written form. Graphemics analyzes the rules and conventions that govern the representation of sounds and meanings through these written symbols, making it crucial for understanding the structure and function of written language.

The other options pertain to different areas of language study. Discourse analysis investigates larger units of language such as conversation and written text, focusing on how meaning is constructed in communication. Sociolinguistics examines the relationship between language and society, including how language varies and changes in different social contexts. Phonetics, on the other hand, is concerned with the physical properties of spoken sounds, rather than the written representation of language. Thus, graphemics is the appropriate field for studying orthographic signs specifically.