Can or Could, Will or would?

Question

What is the difference between "could you tell him that I called" and "Can you tell him that I called"
When do I use "can" and when do I use "could"
The same thing applies to "will" and "would"
What is the difference. Are the all correct, grammartically?

Answer 1

Could is an auxiliary verb, a modal auxiliary verb. We use could to talk about PAST possibility or ability and make requests

Can is an auxiliary verb, a modal auxiliary verb. We use can to talk about possibility and ability and make requests or ask for or give permission

So, you'd say: "Can you tell him that I called."

Same thing with "will" and "would". "Will" is future and "Would" is past.

I will go with you
or
I would have went with you

Answer 2

Referring to one of the answers to this question - NEVER say "I would have went with you..." Perhaps, "I would have GONE with you."

Regarding your first question - "Can" implies the ability to do something, The literal meaning of "Can you tell him that I called?" is "Do you have the ability to relay the message to him about my having called?"

Could is the past of "can" and it can be used to talk about the present and future - conditional. Your example translates into - "If you wanted to, do you have the ability to tell him that I called?"

Will and would are used to ask people to do things. Will you please do that? Would you do that? From a personal perspective I have found that "would" is a subtle way of directing/ordering someone to do something so that it sounds as if they are doing you a favour by doing it. Example: Would you get the candles for the birthday cake?

In closing, I believe the best choice is, "Would you tell him that I called?" And of course, always nice to add a "please".

Answer 3

In the example that you've given, all the possibilities are grammatically correct. However, this example is actually a polite request. You want someone to do something for you. When you're making a request, "could" and "would" are considered more polite than "can" and "will".

Answer 4

can implies ability/capability and so can you do this would mean are you capable of doing this/are you willing to do this
could will imply faith in the ability/capability and is used for politely requesting for a favour.so could you do this would mean i know you can do this.so i will be obliged if you do this for me
will you do this will mean shall i take it that you are willing to do this
would you do this means please do this favour