Well, there’s a custom dictionary file for every user account on your Mac, and were you so inclined, you could go in and add words, names, or anything else you were tired of being corrected on to its list. But what if it keeps trying to correct a word you know is right? I find this happens a lot with technical terms. If you tap the spacebar when you see a suggestion like the one above, your Mac will helpfully insert the correction, and you’ll be on your way. Recent versions of Mac OS X will offer suggestions and automatically correct stuff if you’ve misspelled a word.
