One dictionary I consulted was Random House Unabridged 2nd Edition (circa
1983). I also consulted with a former editor who's a long-time good usage
writing maven, who agreed that it would not be right to hyphenate "dictionary"
with "dictio-" at the end of a line. For other similar words, TeX's
hyphenation databases would seem to agree:
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\documentclass{ltugboat}
\begin{document}
Dictionary, and dictionary, dictionary, dictionary?
Visionary, and visionary, and visionary, visionary.
Evolutionary, evolutionary, volution, evolutionary.
Revolutionary, evolution, evolution, revolutionary.
Foobar, foo, bar, evolution, counterrevolutionary.
Inflationary, inflationary, inflationary, inflationary.
Missionary, missionary, a missionary, missionary.
Reversionary, reversion, reversionary, reversionary.
Cautionary, a cautionary, cautionary, cautionary.
\end{document}
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So what is Webster's rationale for the difference? It seems plainly incorrect.
Doug McKenna