In how many ways can you create a paragraph in LaTeX?

Question

How many ways are there to indicate the beginning of a new paragraph in LaTeX? Only way I know of is the double linebreak.

Answer 1

Neither an empty line nor a \par token indicate the beginning of a new paragraph; they end an active paragraph and switch to unrestricted vertical mode (if the processor has been in unrestricted horizontal mode so far). To begin a new paragraph, either \indent, \noindent or a horizontal command has to be used—i.e., a command that forces TeX to switch to (unrestricted) horizontal mode. Well known horizontal commands are the character-insertion commands such as a, and \unhbox. The full list of horizontal commands is given by §6.2 of TeX by Topic.

Answer 2

Phillip has given a great explanation how paragraphs can be started. Since you question means alternatives to a double line break, which actually doesn't start a paragraph but it ends one, I assume your intention is how to create a paragraph break, i.e. how to end a paragraph.

You could use the command \par instead of two consecutive linebreaks, i.e. instead of an empty line in your source code.

Another possibility is \endgraf, since latex.ltx defines

\let\endgraf=\par

Then, there's ^^M (if active, such as done by \obeylines) and \@@par. Packages could define further aliases and even modify paragraph commands (yes, there's also \@par).

Just scan latex.ltx or source2e to find such commands.

I would recommend to use blank lines or \par, but not other internal commands or shortcuts, to keep your code readable.

Answer 3

An empty line and \par have been already mentioned, but there is more. Quoting The TeXbook, p. 86:

A paragraph also ends when you type certain things that are incompatible with horizontal mode. For example, the command \vskip 1in on line 16 of Chapter 6's story file was enough to terminate the paragraph about ...beautiful documents.; no \par was necessary, since \vskip introduced vertical glue that couldn't belong to the paragraph.