And I'll add that you don't have to know hanja to do this. You just need to be able to judge same vs different. For example, 행복 (happiness) and 다행 (something like "Thank God" or "relief", but literally "fortune" or "luck" or something like that) both have 행, and I speculated that happiness is related to luck/fortune in Korean like in many other languages (for example, English "happy" is related to "happen", opposed to "mishap", etc.). Sure enough, the hanja is the same for each 행. I also noted that 은행 (bank) had this syllable and wondered if it was also related; it seemed like a stretch, but a bank is where you store treasure which could be related with happiness, or it's associated with money, and I thought of the English idiom "to make a fortune" where "fortune" means "a lot of money." So I looked up 은행. As it turns out, totally different hanja. It is not related to fortunate/happy. The point of this example is that you can do this exercise without knowing the hanja. All you have to do is see if it looks the same or not.