could & would? how to use them properly?

[abcd1234]

hi, teachers.

can you teach me how to use properly the could & would words?

thanks in advance.

[Casiopea]

Degree of Politeness Auxiliary
somewhat polite: "Could you tell me ...?"
quite polite: "Would you tell me ...?"

The modal auxiliary could is used

[1] to express an ability in the past:
ex: I could always beat you at tennis when we were kids.

[2] to express past or future permission:
ex: Could I bury my cat in your back yard?

[3] to express present possibility:
ex: We could always spend the afternoon just sitting around talking.

[4] to express possibility or ability in contingent circumstances:
ex: If he studied harder, he could pass this course.

Note that, in expressing ability, can and could frequently also imply willingness: Can/Could you help me with my homework?

"could" Source


The modal auxiliary would is used

[1] to express willingness:
ex: Would you please take off your hat?

[2] to express insistence (rather rare, and with a strong stress on the word "would"):
ex: Now you've ruined everything. You would act that way.

[3] to express characteristic activity:
ex: After work, he would walk to his home in West Hartford. <customarily>
ex: She would cause the whole family to be late, every time. <causal>

[4] to express a hypothetical meaning:
ex: My cocker spaniel would weigh a ton if I let her eat what she wants.

[5] to express a sense of probability:
ex: I hear a whistle. That would be the five o'clock train.

"would" Source