English Grammar: Expressing Future

Study Notes

Using present continuous for plans or arrangements, e.g., "We're having a tea party this afternoon."
Using present simple for something scheduled, e.g., "The train arrives at 6.30 in the morning."
Using "will" to express beliefs about the future, e.g., "I think Brazil will win the World Cup."
Using "be going to" to talk about plans and intentions, e.g., "I'm going to drive to work today."
Using "should" if we think there's a good chance of something happening, e.g., "We should be home in time for tea."

Using "to" to express purpose, e.g., "I am saving money to buy a new car."
Using "so as not to" to express avoidance, e.g., "I'll take the taxi so as not to be late."
Using "so that" to express purpose, e.g., "He whispered so that nobody would hear him."
Using "in order to" to express purpose, e.g., "I am studying hard in order to pass the exam."
Using "for + noun/gerund" to express purpose, e.g., "She is taking Spanish classes for her job."

Using "can" to express ability, e.g., "He can read Arabic."
Using "could" to express past ability, e.g., "He could read Arabic when he was four."
Using "is able to" to express ability, e.g., "She's able to run a marathon."
Using "was able to" to express past ability, e.g., (no example provided)

Using "can" to express possibility, e.g., "He can win the race."
Using "could" or "could have" to express possibility, e.g., "They could still be at school." or "She could have been killed in the car crash."
Using "may" or "may have" to express possibility, e.g., "Tom may be studying in his room." or "He may have spoken to Jenny yesterday."
Using "might" or "might have" to express possibility, e.g., "He might have forgotten."
Using "it is likely" or "it was likely" to express possibility, e.g., "It was likely that he had arrived the day before."

Using "must" to express strong possibility, e.g., "She must be working." (90% certain - positive)
Using "can't" to express strong impossibility, e.g., "She can't be over forty." (negative)
Using "couldn't" to express strong impossibility, e.g., "He couldn't be at work." (negative)
Using "must have" to express strong possibility, e.g., "She must have been working." (positive)
Using "can't have" to express strong impossibility, e.g., "She can't have stolen the money." (negative)
Using "couldn't have" to express strong impossibility, e.g., "He couldn't have been at work yesterday." (negative)

Using "can" or "can't" to express permission, e.g., "You can/can't borrow my car."
Using "could" to ask for permission, e.g., "Could I use your phone?" (more polite)
Using "may" to give permission, e.g., "You may use the phone." (formal)
Using "might" to ask for permission, e.g., "Might I speak to Mr Jones, please?" (more formal)
Using "be allowed" to express permission, e.g., "He wasn't allowed to/couldn't cross the border."