To specify additional conditions where line-breaking is not allowed, customize the abnormal hook variable @code{fill-nobreak-predicate} (@pxref{Hooks}).  Each function in this hook is called with no arguments, with point positioned where Emacs is considering breaking a line.  If a function returns a non-@code{nil} value, Emacs will not break the line there.  Functions you can use there include: @code{fill-single-word-nobreak-p} (don't break after the first word of a sentence or before the last); @code{fill-single-char-nobreak-p} (don't break after a one-letter <del>word); and</del> <ins>word preceded by a whitespace character);</ins> @code{fill-french-nobreak-p} (don't break after @samp{(} or before @samp{)}, @samp{:} or <del>@samp{?}).</del> <ins>@samp{?}); and @code{fill-polish-nobreak-p} (don't break after a one letter word, even if preceded by a non-whitespace character).</ins>