subscript

Etymology

sub- + script

noun

1. (typography) A type of lettering form written lower than the things around it.
   In chemical formulas the number of atoms in a molecule is written as a subscript, so we write H₂O for water which has two atoms of hydrogen for each one of oxygen.
2. (programming) An index into an array or hash.
   If the container is subscriptable and you remember the position where a particular piece of data was stored, you can use the subscript to efficiently retrieve the data. 2012, Robert Robson, Using the STL: The C++ Standard Template Library, page 249

verb

1. (mathematics, sciences, typography, transitive, of a variable) To provide with a subscript.
   As in the chapters on the synchronous model, we use the convention of subscripting a variable by the index of the process at which the variable resides. 1996, Nancy A. Lynch, Distributed Algorithms, Elsevier, page 210
   The elements of these matrices are subscripted with a row–column index, that is, with two integers that give the row and column position in the array. 2011, William M. Davis (original author Cifford E. Dykstra), Physical Chemistry: A Modern Introduction (Second Edition), CRC Press, page 424
2. (mathematics, sciences, typography, transitive, of a text) To convert to a subscript form.
   If your presentation covers chemistry or some other scientific field, you'll need to subscript and superscript characters (think H2O). 2007, Emily A. Vander Veer, PowerPoint 2007: The Missing Manual
3. (programming, transitive) To access (an array element) by its index.
   Avoid subscripting arrays or hashes within loops. 2005, Damian Conway, Perl Best Practices

adj

1. Written underneath.