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Could

"Could" is used to express possibility or past ability as well as to make suggestions and requests. "Could" is also commonly used in conditional sentences as the conditional form of "can."

Examples:

• Extreme rain could cause the river to flood the city. possibility
• Nancy could ski like a pro by the age of 11. past ability
• You could see a movie or go out to dinner. suggestion
• Could I use your computer to email my boss? request
• We could go on the trip if I didn't have to work this weekend. conditional

Using "Could" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "could" behaves in different contexts.

Modal Use	Positive Forms 1. = Present 2. = Past 3. = Future	Negative Forms 1. = Present 2. = Past 3. = Future	You can also use:
could possibility	1. John could be the one who stole the money. 2. John could have been the one who stole the money. 3. John could go to jail for stealing the money.	1. Mary couldn't be the one who stole the money. 2. Mary couldn't have been the one who stole the money. 3. Mary couldn't possibly go to jail for the crime.	might, may
could conditional of can	1. If I had more time, I could travel around the world. 2. If I had had more time, I could have traveled around the world. 3. If I had more time this winter, I could travel around the world.	1. Even if I had more time, I couldn't travel around the world. 2. Even if I had had more time, I couldn't have traveled around the world. 3. Even if I had more time this winter, I couldn't travel around the world.

Could

"Could" is used to express possibility or past ability as well as to make suggestions and requests. "Could" is also commonly used in conditional sentences as the conditional form of "can."

Examples:

• Extreme rain could cause the river to flood the city. possibility
• Nancy could ski like a pro by the age of 11. past ability
• You could see a movie or go out to dinner. suggestion
• Could I use your computer to email my boss? request
• We could go on the trip if I didn't have to work this weekend. conditional

Using "Could" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "could" behaves in different contexts.

Modal Use	Positive Forms 1. = Present 2. = Past 3. = Future	Negative Forms 1. = Present 2. = Past 3. = Future	You can also use:
could possibility	1. John could be the one who stole the money. 2. John could have been the one who stole the money. 3. John could go to jail for stealing the money.	1. Mary couldn't be the one who stole the money. 2. Mary couldn't have been the one who stole the money. 3. Mary couldn't possibly go to jail for the crime.	might, may
could conditional of can	1. If I had more time, I could travel around the world. 2. If I had had more time, I could have traveled around the world. 3. If I had more time this winter, I could travel around the world.	1. Even if I had more time, I couldn't travel around the world. 2. Even if I had had more time, I couldn't have traveled around the world. 3. Even if I had more time this winter, I couldn't travel around the world.

Can

"Can" is one of the most commonly used modal verbs in English. It can be used to express ability or opportunity, to request or offer permission, and to show possibility or impossibility.

Examples:

• I can ride a horse. ability
• We can stay with my brother when we are in Paris. opportunity
• She cannot stay out after 10 PM. permission
• Can you hand me the stapler? request
• Any child can grow up to be president. possibility

Using "Can" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "can" behaves in different contexts.