Could is similar to can in that they both can be used to express ability. Compared to can, could suggests something when describing an ability.
- I could drive you to work. (Let me drive you.)
- I could teach you English. (Let me teach you.)
Could can be used to describe a past ability (the past tense of can).
- I could speak German when I was younger, but since I didn’t practice, I no longer can.
- I could run for miles when I was your age!
Could can be used to politely request something.
Could you pass the bread?
Could you lend me a pencil?
Could can be used to describe a possibility. Compared to will, it is less certain. It is used similarly to might.
- You could catch a cold if you walk out in the cold weather with wet hair.
