Subscript
A subscript or superscript is a number, figure, symbol, or indicator that is smaller than their normal line of type and is set slightly below or above it. Subscripts appear at or below the baseline, while superscripts are above. Subscripts and superscripts are perhaps best known for their use in formulas, mathematical expressions, and specifications of chemical compounds and isotopes, but have many other uses as well.
In professional typography, subscript and superscript characters are not simply ordinary characters reduced in size; to keep them visually consistent with the rest of the font, typeface designers make them slightly heavier than a reduced-size character would be. The distance that sub- or superscripted text is moved from the original baseline varies by typeface and by use.
In typesetting, such types are traditionally called superior and inferior letters, figures, etc., or just superiors and inferiors. In English, most nontechnical use of superiors is archaic. Superior and inferior figures on the baseline are used for fractions and most other purposes, while lowered inferior figures are needed for chemical and mathematical subscripts.
A single typeface may contain sub- and superscript glyphs at different positions for different uses. The four most common positions are listed here. Because each position is used in different contexts, not all alphanumerics may be available in all positions. For example, subscript letters on the baseline are quite rare, and many typefaces provide only a limited number of superscripted letters. Despite these differences, all reduced-size glyphs go by the same generic terms subscript and superscript, which are synonymous with the terms inferior letter (or number) and superior letter (or number), respectively. Most fonts that contain superscript/subscript will have predetermined size and orientation that is dependent on the design of the font.
Perhaps the most familiar example of subscripts is in chemical formulas. For example, the molecular formula for glucose is C6H12O6 (meaning that it is a molecule with 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms).
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