When should you use \vskip (\hskip) rather than \vspace (\hspace) in a LaTeX document?

Question

I assume that, to guard against strange errors, you should use \vspace rather than \vskip whenever possible in a LaTeX document. But are there any situations in which you must use \vskip?

I'm wondering the same thing about \hspace vs. \hskip.

Answer 1

The answer is easy: you should never use \vskip in a LaTeX document. The only precaution to be taken is adding a blank line before \vspace when the vertical space is meant to appear between paragraphs, which usually is the case.

However, \vspace can also appear in a paragraph and the vertical spacing will be applied below the text line where the command finally happens to fall: think of it as an invisible “word” that extends below the baseline (but this space will disappear at a page break anyway).

There are several reasons for not using \vskip (except, maybe, in basic LaTeX programming):

1. it's easy to add a * where needed;
2. it's easy to change \vspace into \addvspace (when two consecutive \addvspace commands, that are usually issued by macros rather than directly, only the largest one prevails);
3. the syntax conforms to the traditional LaTeX one and a \relax is placed by default behind the scenes, thus avoiding some possible problems that, by Murphy's law, will show as very weird errors.

Similarly, never use \hskip in a LaTeX document, but prefer \hspace which avoids head scratching in cases such as

text\hskip 1pt plus other text

Try it. ;-) Then you'll switch to

text\hspace{1pt}plus other text

Notice that \hspace{...} should not be preceded nor followed by a space, because we're overriding TeX's rules at that point and we probably don't want other spaces to begin with.

Answer 2

If you are an author of the text, you should never use \vspace nor \vskip because you should use only logical markup of the document. And typographical issue is responsibility of used macros.

If you are macro programmer then you like TeX primitives like \vskip, \vadjust, \hskip because you understand well what they are doing. And you needn't to use a complicated macros like \vspace in your macros.

The result: there is no need to use \vspace.

Moreover, \vspace is a big source of user confusions, because its default behaviour is something like \vadjust{\vskip...} so, it breaks line grid in the current paragraph but it doesn't end the paragraph.

Answer 3

One difference that appears strange to me is, that \hspace does not eat following spaces:

Test\hskip0.1\textwidth\relax Test

Test\hspace{0.1\textwidth} Test

Test\hspace{0.1\textwidth}Test

Thus, in many low level cases \hskip is preferred. This appeared to me when implementing something similar to another question.