can-can

Modal Use	Positive Forms 1. = Present   2. = Past   3. = Future	Negative Forms 1. = Present   2. = Past   3. = Future	You can also use:
can general ability	1. I can speak Chinese. 2. SHIFT TO "COULD" I could speak Chinese when I was a kid. 3. SHIFT TO "BE ABLE TO" I will be able to speak Chinese by the time I finish my course.	1. I can't speak Swahili. 2. SHIFT TO "COULD" I couldn't speak Swahili. 3. SHIFT TO "BE ABLE TO" I won't be able to speak Swahili.	be able to
can ability during a specific event	1. With a burst of adrenaline, people can pick up cars. 2. SHIFT TO "BE ABLE TO" With a sudden burst of adrenaline, he was able to lift the car off the child's leg. 3. SHIFT TO "BE ABLE TO" With a sudden burst of adrenaline, he will be able to lift the car.	1. Even with a burst of adrenaline, people can't pick up something that heavy. 2. SHIFT TO "BE ABLE TO" Even the weight lifter, wasn't able to lift the car off the child's leg. 3. SHIFT TO "BE ABLE TO" Even three men working together won't be able to lift the car.	be able to
can opportunity	1. I have some free time. I can help her now. 2. SHIFT TO "BE ABLE TO" I had some free time yesterday. I was able to help her at that time. 3. I'll have some free time tomorrow. I can help her then.	1. I don't have any time. I can't help her  now. 2. SHIFT TO "BE ABLE TO" I didn't have time yesterday. I wasn't able to help her at that time. 3. I won't have any time later. I can't help her then.	be able to
can permission	1. I can drive Susan's car when she is out of town. 2. SHIFT TO "BE ALLOWED TO " I was allowed to drive Susan's car while she was out of town last week. 3. I can drive Susan's car while she is out of town next week.	1. I can't drive Susan's car when she is out of town. 2. SHIFT TO "BE ALLOWED TO " I wasn't allowed to drive Susan's car while she was out of town last week. 3. I can't drive Susan's car while she is out of town next week.	may
can request	Can I have a glass of water? Can you give me a lift to school? Requests usually refer to the near future.	Can't I have a glass of water? Can't you give me a lift to school? Requests usually refer to the near future.	could, may
can possibility, impossibility	Anyone can become rich and famous if they know the right people. Learning a language can be a real challenge. This use is usually a generalization or a supposition.	It can't cost more than a dollar or two. You can't be 45! I thought you were about 18 years old. This use is usually a generalization or a supposition.	could  http://en.wikipedia.org/wiki/English_modal_verbs