Chapter 4 describes the fundamental components of historical writing systems, in order to provide a first compendium of definitions immediately relevant to historical orthography. The chapter begins with an overview of different types of writing systems, covering similarities and differences between pictograms, ideograms, syllabaries and alphabets. The discussion then focuses in greater detail on alphabetic orthographies, defining basic elements in historical writing systems that can work as individual foci of analysis or can combine together for a broader empirical perspective. These elements are defined in this chapter under the following categories: graphemes and allographs, letters, graphs, characters and glyphs, punctuation and capitalisation. Within these general categories, my discussion also covers definitions and examples for terms like graphemic inventories and word division which are conceptually related to the elements above. The graphemic inventory of a writing system consists in the full collection of graphemes used in a specific language where the writing system is used. The expression word division indicates the ways in which words in historical texts usually appear, i.e. joined, hyphenated or separated.