Interactively...

Make a selection, then choose styles from the Format menu. Common style operations have keyboard shortcuts: for bold, for italic and / to make text larger/smaller:

Programmatically...

Use Style in input expressions to produce styled outputs:

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With a Custom Button...

Make a styling button

Make a button that italicizes and highlights selected text:

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Use the button

Use the button to highlight text:

  • Custom buttons are useful for making styling toolbars. See Set Up a Docked Cell for more information.

Interactively...

Open the Formatting panel

Choose Format in the menu bar to open the Formatting panel in the sidebar:

Select the text you want to style

Mouse down and drag to select the text you want to apply styling to:

  • To select complete words when you drag, double-click a word when you mouse down.

Style the selected text

Increase the size of the text:

Make the text red:

Programmatically...

Use Style in input expressions to produce styled outputs:

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  • Styles added to input expressions via the formatting panel are removed upon evaluation.

Notes

Styles in input expressions do not affect evaluation.
To make style changes that affect an entire notebook, it may be more efficient to change the notebooks stylesheet than to make individual style changes. See Choose a Stylesheet for a Notebook for details.