say "[line break]"

This text substitution produces a line break. Example:

"There is an endless sense of[line break]falling and[line break]falling."

Line breaks are not paragraph breaks, so the result is:

There is an endless sense of
falling and
falling.

with no extra vertical spacing between these lines.

say "[no line break]"

This text substitution produces no text. It's used only for a side-effect: it prevents a line break where Inform might otherwise assume one. Example:

"The chorus sing [one of]Jerusalem[or]Rule, Britannia![no line break][at random]."

Here the "[no line break]" stops Inform from thinking that the exclamation mark means a sentence ending - it's part of the name of the song "Rule, Britannia!". So we get

The chorus sing Rule, Britannia!.

with no line break between the "!" and ".".

say "[run paragraph on]"

This text substitution produces no text. It's used only for a side-effect: it prevents a paragraph break occurring after the present text is printed, in case Inform might be tempted to place one there. Example:

Before taking something, say "Very well. [run paragraph on]".

This allows the reply to, say, TAKE ENVELOPE to be

Very well. Taken.

rather than

Very well.

Taken.

which is how texts produced by different rules would normally be shown. (It's a traditional printer's term. See Oldfield's Manual of Typography, 1892, under "When two paragraphs are required to be made into one, or, in technical language, 'to run on'.")

say "[paragraph break]"

This text substitution produces a paragraph break. Example:

"This is not right.[paragraph break]No, something is terribly wrong."

Paragraph breaks have a little vertical spacing in them, unlike mere line breaks, so the result is:

This is not right.

No, something is terribly wrong.

say "[conditional paragraph break]"

This text substitution either produces a paragraph break, or no text at all. It marks a place where Inform can put a paragraph break if necessary; in effect it simulates what Inform does every time a "before" or similar rule finishes. If there i text already printed, and text then follows on, a paragraph break is made. But if not, nothing is done. This is sometimes useful when producing a large amount of text which changes with the circumstances so that it is hard to predict in advance whether a paragraph break is needed or not.

if a paragraph break is pending:

This condition is true if text has recently been said in such a way that Inform expects to add a paragraph break at the next opportunity (for instance when the present rule ends and another one says something, or when a "[conditio al paragraph break]" is made).

say "[command clarification break]"

This text substitution produces a line break, and then also a paragraph break if the text immediately following is a room description brought about by having gone to to a different room and looking around, in which case a line break should be dded. In traditional IF, this is used when clarifying what Inform thinks the player intended by a given command. Example:

say "(first opening [the noun])[command clarification break]";

might result in

(first opening the valise)
You rummage through the valise for tickets, but find nothing.

say "[run paragraph on with special look spacing]"

This text substitution produces no text. It's used only for a side-effect: it indicates that the current printing position does not follow a skipped line, and that further material is expected which will run on from the previous paragraph, but that if no furt er material turns up then a skipped line would be needed before the next command prompt. (It's very likely that only the Standard Rules will ever need this.)