How do I change the font of a subformula?

How do I change the font of a subformula?

You can use one of the following font attributes:

• italic a typesets a in italic shape.
• so does ital a.
• nitalic a typesets a in upright shape (abbreviation for not italic).
• bold a typesets a in boldface.
• nbold a typesets a with normal weight (abbreviation for not bold).

In addition Math uses a set of three generic font families, which are used as follows:

• font serif a typesets a in a serifed font, usually Times.
• font sans a typesets a in a sans serif font, usually Helvetica or Arial.
• font fixed a typesets a in a fixed font, usually Courier.

Font attributes can be combined as in this example:

• Enter bold font sans A to get A.

You can apply font attributes to an entire subformula if you group it with { } or other brackets. Example:

• Enter a b bold {c d} e to typeset abcde.

When several font attributes are applied, the innermost takes precedence as shown in this example:

• Enter bold {a b nbold c d} to get abcd.

To change the fonts used in Math see How do I change the fonts used in my formula?