1. ability
2. permission
3. theoretical possibililty - Anybody can make mistakes. The road can be blocked (it is possible to block the road).
1. past ability
2. present or future permission
3. present possibility (theoretical or factual) - We could go to the concert. The road could be blocked.
4. possibility or ability in UNREAL conditions - If we had more money, we could buy a car.
1. permission
2. possibility (factual) - The road may be blocked (it is possible that the road is blocked).
1. permission (rare)
2. possibility (theoretical or factual)
1. willingness (2nd or 3rd person) - He shall get his money.
2. intention (1st person) - We shall overcome.
3. insistence - You shall do as I say (I insist on it).
1. obligation
2. logical necessity
3. after certain expressions - It's odd that you should say that. I'm sorry that this should have happened.
4. in normal real conditions - If you should change your mind, please let us know.
1. willingness (in polite requests)
2. intention (usually contracted) - I'll write as soon as I can.
3. insistence (no contraction) - We will do it, whatever you say (He insists on it).
4. logical necessity - The game will be over by now.
5. habitual present - Oil will float on water.
6. future
1. willingness
2. insistence - He would do that (he insists on it).
3. characteristic activity in the past
4. unreal condition - He would smoke too much it I didn't stop him.
5. probability - This would be his mother.
1. oblligation
2. logical necessity