the things i didn't know. you have to meet Tom tonight for watching movie and then someone ask you "why don't you coming to party tonight?" , in this situation, how can you say? i usually have said "sorry, i have a appointment" or "i have a meeting" finally, i got to know it was wrong expression. when i have to meet dentist or doctor, i can use 'appointment'. and when i have to go to office, or official gathering, i can use 'meeting' when i have to meet friends or go private gathering, i can use 'i have a plan' i learned expression "i have a plan." that is the thing i didn;t know