The term "digraph" has been employed in literature to describe a pair of characters that combine to represent a single phoneme, as illustrated in discussions of early alphabets. For instance, as noted in [1], the Anglo-Saxon alphabet included two distinct symbols for the "th" sound—symbols that did not survive into later forms of English. This usage underscores the historical significance of digraphs in the evolution of writing systems, highlighting how specific letter combinations were once fundamental to phonetic representation, even if later replaced or modified in modern orthography.