Everyone knows how to look up unfamiliar words in a dictionary. But hauling out a dusty tome and flipping through pages of tiny text is so last century. It’s far simpler to use the Mac’s built-in dictionary, especially when you use our favorite ways of accessing it. Assuming that the word is showing on your screen, (1) mouse over it and press Command-Control-D, (2) Control/right-click it and choose Look Up “word”, or (3) use a gesture defined in System Preferences > Trackpad > Point & Click, under “Look up & data detectors.” A popover appears, showing the word’s definition. It may also show a thesaurus entry, and in some cases, you’ll see a Wikipedia entry.