# When to use \par and when \\

What is the difference between `\par` and `\\` and when should I use `\par` instead of `\\`?

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Well, use `\par` when you want a new paragraph (and don't wan to insert a blank line for some reason, such as in macro/environment definitions), and use `\\ ` in `array` and `tabular`. That's the rules I have been following. –  Peter Grill Nov 14 '12 at 0:57

`\par` is a Tex primitive and is the same as a blank line (except in special environments such as `verbatim` where the usual rules don't apply). It ends horizontal mode, causes TeX to break the horizontal text into lines placed on the current vertical list, and exercises the page breaker which may possibly cause the next page to be shipped out.

`\\` is different in almost every respect. It is a macro not a primitive, and its definition changes wildly in almost every LaTex definition. The definition in normal text, a `center` environment a `flushleft` environment and a table are all different.

In normal running text when it forces a linebreak it is essentially a shorthand for `\newline` this does not end horizontal mode or end the paragraph, it just inserts some glue and penalties at that point into the horizontal material so that when the paragraph does end a linebreak will occur at that point with the short line padded with white space.

You should rarely need to use `\\` in documents apart from its use in alignments (where it is a macro based on the `\cr` primitive), and you should rarely need `\par` in documents as a blank line should suffice.

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a consequence of using `\\ `instead of paragraph breaks is that (la)tex continues to load text into memory, and doesn't actually output anything until an actual paragraph break occurs. this may not be so important now, with memory capacity being so large, but when memory was a much more scarce resource, failing to use paragraph breaks was a sure way to run out of memory and crash the job before it finished. it will still slow down the processing when the "paragraphs" are very long. –  barbara beeton May 2 at 1:39

In text mode, `\par` starts a new paragraph, while `\\` ends the current line.

So when to use each one?

`\\` should be used with parsimony, when you want to break of the rhythm of your current argumentation, but without jumping to a new idea / argument (which would require starting a new paragraph).

`\par` should actually be used even less frequently. Not that you do not want to start new paragraphs (you do want to keep paragraphs to reasonable lengths!), but you should start new paragraphs by leaving an empty line in your TeX code. This has the exact same effect as using `\par`, but will make your code much more readable. `\par` is therefore mostly used when defining macros.

Note that outside of text mode, `\par` will usually lead to an error, while `\\` usually works as expected to start a new line (like while in an `tabular` or `array`).

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