Forceable vs. Forcible

library shelfMicrosoft Word 2003 tried to tell me today that forceable in the phrase forceable input should read forcible. But I’ve never been one to take Word’s word for anything. I checked a few online dictionaries and received little guidance. Most didn’t list forceable. Those that did, however, didn’t indicate that it was a variant of forcible.  Only that it was the adjective form of force. So what’s the relationship between these two words? Is forcible the preferred spelling?

Thank goodness for Bryan Garner. In Modern American Usage, he explains that forceable is not, in fact, a needless variant. Forcible means “effected by physical force against resistance,” as in forcible entry. By contrast, forceable simply means “able to be forced.” So in technical writing, an input that can be forced to change state is forceable.

Fowler’s Modern English Usage highlights other words where the meaning changes depending on whether the -able or -ible suffix is used. For instance, a disease is contractable, but elastic is contractible. Tea is infusable (infuse+able), while rubies are infusible (in+fusible). Many dictionaries seem to be losing these subtle distinctions, choosing one spelling or the other for both meanings. Let’s hope that Microsoft Word doesn’t become the ultimate arbiter.