In reality most fonts that include these characters ignore the Unicode definition, and design the digits for mathematical numerator and denominator glyphs, which are smaller than normal characters but are aligned with the cap line and the baseline, respectively. Thus 'H₂O' (using a subscript character) is supposed to be identical to 'H 2O' (with subscript markup). The intended use when these characters were added to Unicode was to allow chemical and algebra formulas and phonetics to be written without markup, but produce true superscripts and subscripts. 3 Other superscript and subscript characters.