Text Formatting and Punctuation

A formatting mark is a symbolic character, such as *, _, or ~, that indicates the inline style you want Asciidoctor to apply to the text. Formatting marks come in pairs.

A formatting pair consists of an identical opening mark and closing mark that encloses the text you want to style.

The opening mark specifies where you want the style to start. The closing mark specifies where you want the style to end.

A formatting pair is defined as either constrained or unconstrained, depending on where it’s allowed to be applied. An unconstrained pair can be applied anywhere, whereas the application of a constrained pair is more limited.

When a blank space directly precedes the text to format, and a blank space or punctuation mark (,, ;, ", ., ?, or !) directly follows the text, a constrained formatting pair can be used. A constrained pair uses a single opening mark and a single closing mark to enclose the text to be styled (e.g., *strong*).

For example, you use this form to format a word that stands alone,

to format a sequence of words,

or to format a word adjacent to punctuation, like an exclamation mark.

As you can see, the constrained pair offers a more succinct markup at the tradeoff of having more limited (constrained) use. However, it should suffice in most cases, so the abbreviated markup is a benefit. You can think of a constrained pair as being a weaker markup than an unconstrained pair.

When a blank space does not precede the text to format, or a blank space or punctuation mark (,, ;, ", ., ?, or !) does not directly follow the text, or the text does not start or end with a word character, a unconstrained formatting pair must be used. An unconstrained pair uses a double opening mark and a double closing mark to enclose the text to be styled (e.g., Sara**h**).

For example, you’d use an unconstrained pair to format just one or a few letters in a word.

The unconstrained pair provides a more brute force approach to formatting at the tradeoff of being more verbose. You’ll typically switch to an unconstrained pair when a constrained pair doesn’t do the trick. See When should I use an unconstrained pair? for more examples of when to use an unconstrained pair.