chance : 侧重指偶然或意外的机会，有时也指正常或好的机会。
- I didn't get/have a chance to speak to her.
- If you give me a chance to speak, I'll explain.
- Society has to give prisoners a second chance when they come out of jail.
- He left and I missed my chance to say goodbye to him.
- I'd go now given half a chance (= if I had the slightest opportunity).
opportunity : 侧重指有利或适合于采取行动，以达到某一目的或实现某种愿望的最佳时机或机会。
- Everyone will have an opportunity to comment.
- I was never given the opportunity of going to college.
- The exhibition is a unique opportunity to see her later work.
- An ankle injury meant she missed the opportunity to run in the qualifying heat.
- Please contact us at the earliest opportunity (= as soon as possible).
- He goes fishing at every opportunity (= as often as possible).
- I used to love going out dancing, but I don't get much opportunity now.
- He had a golden (= an extremely good) opportunity to score in the first half but squandered it.
occasion : 指特殊时机或良机，也指时节。
- The 200th anniversary of Mozart's death was the occasion for hundreds of special films, books and concerts.
- An occasion may arise when you can use your knowledge of French.
- The bride took/used the occasion to make a short speech.