This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
 Mathematica Tutorial

Typing Subscripts

Typing xi

Type the symbol that will have the subscript.
Type x.
Create a subscript by pressing the Control key and the - key at the same time.
Press Ctrl+- or Ctrl+_.
Type the subscript into the placeholder (which is already selected).
Type i.
Move the insertion point out of the subscript position up to the baseline by pressing the Control key and the Space bar at the same time.
Press Ctrl+Space.

Typing xi j

Type the symbol that will have the subscript.
Type x.
Create a subscript by pressing the Control key and the - key at the same time.
Press Ctrl+- or Ctrl+_.
Type the subscript into the placeholder (which is already selected).
Type i.
Press the Space bar and then type j.
Press Space and type j.
*To avoid multiplying the two subscripts, separate them with an invisible comma. To type the alias for an invisible comma, press the Escape key before and after typing a comma.
Press Esc, type a comma, press Esc, and type j.
Move the insertion point out of the subscript position up to the baseline by pressing the Control key and the Space bar at the same time.
Press Ctrl+Space.

Typing x23

Type the symbol that will have the subscript.
Type x.
Create a subscript by pressing the Control key and the - key at the same time.
Press Ctrl+- or Ctrl+_.
Type the subscript into the placeholder (which is already selected).
Type 2.
To avoid multiplying the two subscripts, separate them with an invisible comma. To type the alias for an invisible comma, press the Escape key before and after typing a comma.
Press Esc, type a comma, press Esc, and type 3.
Move the insertion point out of the subscript position up to the baseline by pressing the Control key and the Space bar at the same time.
Press Ctrl+Space.

Typing xni

The first three steps create and fill in the subscript and its subscript.
Type x, then press Ctrl+_.
Type n, then press Ctrl+_.
Type i.
Press the Control key and the Space bar at the same time twice to get up to the baseline.
Press Ctrl+Space twice.