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19.6 ~, \nobreakspace ¶

Synopsis:

before~after

The tie character, ~, produces a normal word space between before and after at which the line will not be broken. The command \nobreakspace and the Unicode input character U+00A0 are synonyms. The character is also included in Latin 1 and other 8-bit encodings.

The amount of space inserted is exactly the same interword glue as that inserted by a space character between two regular words or the ‘\ ’ command (see Backslash-space: ‘\ ’), which is normally defined by the current font. It can stretch or shrink as usual. The difference is that TeX will not break a line at that space.

The word ‘tie’ has the above meaning in the TeX community; this differs from the typographic term “tie”, which is a diacritic in the shape of an arc, called a “tie-after” accent in the TeX world: o͡o (see Accents).

Here LaTeX will not break the line between “Donald” and “E.”:

Thanks to Donald~E. Knuth.

In addition, despite the period, LaTeX does not use end-of-sentence spacing (see \@).

Ties prevent a line break where that could cause confusion. They still allow hyphenation (of either of the tied words), so they are generally preferable to putting consecutive words in an \mbox (see \mbox & \makebox).

Exactly where ties should be used is something of a matter of taste, sometimes alarmingly dogmatic taste, among readers. If you are using a particular style guide, then of course you should use its particular recommendations. Here are some widely accepted examples, many of them from The TeXbook.

• Between an enumerator label and number, such as in references: Chapter~12, or Theorem~\ref{th:Wilsons}, or Figure~\ref{fig:KGraph}.
• When cases are enumerated inline: Typography involves (1)~technology, and (2)~art.
• In a series: See figures~1, 2, and~3; including math: $1$,~$2$, or~$3$.
• Between a month and day number in a date: October~12 or 12~Oct. In general, in any expressions where numbers and abbreviations or symbols are separated by a space: 565~CE, or 2:50~pm, or Boeing~747, or 268~Plains Road, or \$$60$~kW. Some people prefer a thin space (see \thinspace & \negthinspace) in some of these cases, or no space at all. Whether a tie is used when a unit is spelled out in full, as in 100 meters, is a judgement call, and may depend on context.
• When abbreviations are separated by a space: D.~E. Knuth. Here again some people prefer thin spaces or no space.
• Between a person’s given names and between multiple surnames: Donald~E. Knuth or Luis~I. Trabb~Pardo or Charles~XII—but you must give TeX places to break the line so you might do Charles Louis Xavier~Joseph de~la Vall\'ee~Poussin.
• In various mathematical constructions:
  • When mathematical phrases are rendered in words: equals~$n$, or less than~$\epsilon$, or given~$X$, or modulo~$p^e$ for all large~$n$ (but compare is~$15$ with is $15$~times the height).
  • When a symbol is a tightly bound object of a preposition: of~$x$, or from $0$ to~$1$, or in common with~$m$.
  • Between mathematical symbols in apposition with nouns: dimension~$d$.

If in doubt, you might ask yourself whether the reader would be confused or startled (probably only momentarily, but still) if the space in question became a line break. If yes, use a tie.

Some non-English typesetting traditions have additional strong rules for using ties: in Czech, for example, ties must be placed after single-letter conjunctions; in French, before “high” punctuation marks such as ‘:’; and conventions for breakable vs. unbreakable spaces around em-dashes vary widely. LaTeX can take care of some of these language-specific typesetting with the babel, polyglossia, or other packages, but it can’t do everything.