Did you spot the typo in the header? Spotting weird typos can depend on several things: What font is being used. Some fonts offer plenty of white space between letters; others run them together, which makes weird typos like this much harder to notice. How involved were you in the reading. Perhaps, like me, you tend to gloss over unimportant stuff like chapter headings - let me get to the story! If you already know what the words should say (if you're the author perhaps), why would see something different from what you expect? And of course, if the words are deep in a complex plot or argument, your brain may be just too busy understanding what's going on to spot what's not. Creating weird typos depends on several things too: Perhaps you typed "moderm" instead of "modern" and spell-check made the wrong guess. Perhaps you scanned in a document, and image-to-text failed to see the white space betweeen r and n. Perhaps you used text to speech ...