Will do: it is certain he do it in future.

Would do: it is certain he decide to do now or in future it if he has ability to do and/or knows about it and/or nothing else stop him.

Would have done: it is certain he decide to do in past if he had ability to do and/or knew about it and/or nothing else stop him.

Can do: he have ability to do now or in future.

Could do: he have ability to do now or in future if he decide to do and/or no external condition that stops it being done.

Could have done: he had the ability, he didn’t do in past (maybe there are reasons).

would = intent to do if there is ability.
could = ability to do if there is intent.

• intent: the desire to do and/or the knowledge that it needs to be done and/or no external condition that stops it being done.

“would you like coffee” = If I give to you ability to drink coffee right now, what is your answer, Yes or No?

“I would do it” = If nothing stops me and I have the ability to do, then I do it. This is said with knowledge that some condition must be met before you can do it:
“I would drink that coffee if you give it to me.”
It is letting the listener know that you intend to do action, but it first requires some other thing to happen which gives you ability.

Would is a hypothetical will. “Would you dance” is a general query, but “will you dance” is a call to action. A lot of the time, would is followed by if, as in, “would you dance if I asked you to?”

“Would you like coffee” is a round-about way to ask if you want coffee. Full form would be “if I brought you coffee, would you like it?”

Past tense is “would have”, such as “would you have liked coffee?” This is generally a missed opportinuty where you didn’t do something, and you’re asking so you can know more for the future. Saying “I would have” generally means “I didn’t.”

Would: https://www.dictionary.com/browse/would
• a simple past tense and past participle of will
• used to express an intention or inclination
• used to express an uncertainty
• used in conditional sentences to express choice or possibility

Could: https://www.dictionary.com/browse/could
• a simple past tense of can
• used to express possibility
• used to express conditional possibility or ability
• used in asking for permission

Would / will is used when something is possible but you’re not sure.
Could / can is used when you’re not sure if something is possible. –

Could is maybe-can: I bet I could jump over that car [if I wanted to].

As opposed to I bet I can jump over that car [and I’m going to try].

Would is maybe-will: If you saw an alligator, would you run away?

---

Would is also ‘did’, for habitual actions. When I was young, I would wait by the window for my father to come home.

I would love to help you, but I couldn’t possibly do that.

😋

You’re probably gonna get a better technical answer in !linguistics@mander.xyz on language questions.

It’s not dealing with the past, but with things that don’t happen or might not happen.

Does this answer your question? It’s probably better than an ad-hoc explanation.

https://www.britannica.com/dictionary/eb/qa/How-to-Use-Could-Would-and-Should

Consider the difference between “would do” and “could do” to be the same as “will do” and “can do”, respectively.

One implies action, the other implies capability.

There’s also “should”, which implies permission.

Consider, also, the progress of learning Python (programming language):

1. Could I do this in Python?
2. I would do this in Python.
3. I shouldn’t do this in Python.

Edit to add: Would, could, and should are usually considered future-tense. But add “have” and it’s past-tense…“I would have done that”

“Would” is a very confusing word in English. It can mean opposite things, but native English speakers don’t usually notice how confusing it is.

“Would you?” can be a polite way of asking asking a question. “Would you like some coffee?” is basically the same as “Do you want some coffee?” but a little gentler. It implies more permission to say no.

You say yes to a “would you” question by saying “I would,” or, “yes, I would.”

EXCEPT

“I would” can also be a polite way of saying no. It means that the answer would be yes under some different circumstance. Someone might say “I would have some coffee, but I’m avoiding caffeine.” This is like saying, “Under a different circumstance I’d gladly accept your offer.”

So if I ask “would you like some coffee?” and you say “I would.” That means yes. If you say “I would, but I just had some.” That means no.

Many English learners find this extremely confusing, for good reason.

Let’s see if I can give at least something understandable. To start with, definitely not past tence.

If you ask “would you like coffee?” you’re asking in the present if coffee is something the person wants to drink now. If you ask “would you go to the store?” you are asking if the person doesn’t mind going to the store.

Could is similar but is slightly different, is to ask if the person can do something.

Could you take out the trash ? - are you able to take out the trash?

Would you take out the trash? - do you mind taking out the trash?

Not sure this helps, but in project management there’s this think called the MoSCoW scale to define how important a requirement is, it looks like:

Must (you have to do it)

Should (very important but not as important)

Could (not important but if you can you should do it)

Would (would like to have, this is definitely not important but if you have enough time it’d be great)

They don’t have their own meaning. They modify the tense and mood of the sentence. In many languages, this is built into the verb but English doesn’t have that power. As a result, you have to use external modifiers.

If you won’t, then you can’t because mental barrier, but if you can’t maybe you would if you could.

Regarding your question about being the past tense, they are also used that way. But you also need to make other changes.

Would you like coffee?

This is not about the past. As others have said, this is an offer of coffee. The response is

Yes I would. / No I wouldn’t.

(Or any other acceptance of an offer)

Would you have liked coffee?

This is about the past. It means something like…“Before, is it possible that you wanted coffee?”

It’s a little tough to explain. But a person might ask that question if invited a friend to a café, got there before the friend, and ordered two teas…then the friend looked disappointed about having a tea. “Sorry, do you not like tea? Would you have liked coffee instead?”

The answer here is

Yes I would’ve. / No I wouldn’t have.

It’s a similar situation for “could”.

Could you take out the trash?

This is a request. As others have said, “would” could also be used as a request here, but it’s not very common (at least like this).

Literally, I think it’s a question of capability. I think “could” means “is it possible for X to happen”…but we use it to be a request because of politeness. English speakers don’t think about it this way when making a request, but it will help understand what it means in the past.

Could you have taken out the trash?

This is a question about a past capability. It means something like…“Before, was it possible that you were able to take out the trash?”

You’d ask this if your kid didn’t take out the trash and you want to know if it was possible (with the implication being that you want to know WHY).

The kid would answer

Yes, I could’ve, but …

Or

No, I couldn’t have, because …

Or

Not now mom/dad, I’m playing a game

As you can see, using would/could in the past is possible, but complicated. “Should” is also usable in the past.

Should I wear a hat?

… Is a question about whether you need a hat (maybe before going outside for a walk).

Should I have worn a hat?

…is a question about whether you needed to wear a hat before. Maybe you didn’t wear a hat and got a sunburn on your scalp. Ouch! Yes, you should’ve worn a hat.

I’m not an English teacher but here’s a way of trying to understand these.

would can have various forms, but as used here “would you like coffee?” is not asking if you liked in the past, it’s rather if you want now (or in the future) in a slightly more polite form. Would is a conditional. “would you take the blue or the red pill?” It’s giving you a choice.

Can/could ask more about intent and whether you’re able to do something. “Can you do X?” (Or could you do X? Is the same but a bit more formal). Is asking if the person is capable and wants to do something. “Would you do something?” Gives the person the conditional of either doing something else or just not doing it. It’s a question with an “or else …”.

Could is also the past form of Can. “I could have done it (in the past) but I did not do it” vs. I can do it (now or in the future).

Hope it gives you a starting point!

To give you a final example using various forms:

“You could have Googled this, but you wouldn’t want to waste time scrolling to the useless AI results, which I perfectly understand; we can’t spend all day reading AI generated text.”

As a native English speaker, these questions make me wish we all spoke Latin 😂

I’m not a linguist, but here’s how I understand it:

This is why would is so fucked: it’s used both in the conditional, and the subjunctive mood. However, nothing I see in the online resources really talks about would being used in the subjunctive.

When someone uses the phrase “would you like a coffee?” I’m nearly certain that it’s the subjunctive, polite way of saying “do you want coffee.” It’s very similar to the Spanish quieres/quisieras pair. In Spanish you get an irregular conjugation, but in English, the whole verb changes from to be to will.

As a non-linguist, native speaker, these mood changes come naturally to me. I never had to study them. As a second language learner, this is always one of the most brain-melting facets of a new language.

Edit: “do you” obviously isn’t exactly using the verb to be. I’m not sure what to call that expression. It seems like it could be its own post. This is giving me a headache. This post gets into it, but doesn’t really give the specific answers that I suspect you’re looking for.