Depression and Dejection mean the same thing but depression is more comonly used.
Chance- means there is a possibility but it is not certain. Example... " there is a chance I could win the lottery but it is not certain that I will".
Opportunity- an appropriate time or situation to do something. Example... "meeting my english friend gave me an opportunity to pratice my english"
Toilet is a word used for a restroom you could also use, loo, public convenience, or lavatory there are many words but toilet or restroom are the most polite ones to use :)
Hope this helps :)