Apple makes it easy to look up information about nearly any word you can see on your Mac, in nearly any app. To access this information, Control- or right-click the word and choose Look Up “word”, use the trackpad to tap the word with three fingers, or if you have a trackpad with Force Touch (2015 MacBook/MacBook Pro or later), deep click on the word. macOS displays a popover with a dictionary definition. And in 10.12 Sierra and later, you can also swipe right with two fingers on the trackpad (or click the buttons at the bottom) to see much more in the popover, including Wikipedia entries, apps, news, sports info, movies, TV shows, music, maps, Twitter accounts, and more. Give it a try a few times, and it might become a habit!