Here’s a tip for you. For the usage of Chinese characters, look at Daum Dictionary and click on “한자” and on 관용어 / 학습. From there click on 복합어 . 숙어 and you get what is nearly a comprehensive list of the Korean words using that hanja. I’m not sure, but I assume they put the words in order of frequency too. They also give you the number of instances of that character in Korean words, and this word comes up more than any other I’ve ever seen. Hence, just like the nouns “thing” or “stuff” in English, this character is used extremely frequently.
물건 (mul-geon) – products
물가 (mul-ga) – the price of things (consumer prices)