If you look at customer reviews of recent versions of Microsoft Word, you'll find those reviews divided between users who are tearing their hair out over Word's instability and users who are having no trouble at all. But what's more interesting is how they're divided. Those having trouble are generally those who have used Word for many years. Those having no trouble are the newbies.
That's because the problem often isn't in the app itself. Chances are, it's in the fonts on your computer.
Word comes with a large number of fonts, and over the years, it has changed where it places them on your drive. During these same years, Apple has licensed a number of Microsoft fonts to include in OS X, placing them in yet another location. The upshot is that a long-time Word user can easily have three or more copies of a font in different versions and in different locations, resulting in conflicts. What's more, Word caches the fonts it finds in your system, and that cache can easily become outdated or corrupt. And it doesn't help that many users collect free or cheap fonts that are simply defective.
To stabilize Word, then, your first task is to eliminate duplicate fonts, as well as to discard defective ones. For this, you can use the Mac's Font Book app. Other aids are the Office font management guide at OfficeforMacHelp.com, and the more general reference "Font Management in OS X," by Kurt Lang.
After resolving all font issues, your final step is to zap Word's font cache, so that it will be automatically rebuilt. You can search out the locations of the cache files to delete them manually, but there are also several utilities that can more easily do it for you. Personally, I use TinkerTool System, deleting the cache as part of a regular routine of monthly maintenance.
If you do that, you might be surprised to discover how stable Word really is!