계란, 달걀, 알 --> when to use what??
I haven't got a complete answer for you but I can say that "알" just means 'an egg'.. 'some kind of egg' (could be a dragon egg), whereas 계란 and 달걀 (닭알) refer to
chicken eggs. Typically when I think of food, talk about food, or order food, I seem to find myself using 계란 e.g. 삶은 계란, 계란 후라이, 등등 --the only time I think I ever used 달걀 was when the person looked at me puzzled as if they didn't understand my pronunciation and maybe I said 달걀 말이에요! ㅋㅋ