Decomposition Type - Sub

Sub is a decomposition type indicating that a character should be treated as a subscript form, typically rendered smaller and lowered relative to the baseline of surrounding text, as seen in mathematical notation or chemical formulas. When a character carries this value, its canonical decomposition maps it to a base character, but the subscript formatting is not encoded semantically in the text itself; instead, it reflects a purely visual or typographic distinction. This means that systems using such decompositions must handle the subscript styling separately, since the base character loses the original subscript intent once decomposed. Sub is distinct from other vertical alignment types like super, and it applies to characters such as subscript digits, letters, and specific symbols, ensuring that their usage is recognized as a stylistic variant rather than a distinct meaning.