‘Would’ is both the past tense and the conditional form of the word ‘will’. As a verb, ‘will’ is used to express that something is going to happen in the future, though it can be used for more complex tenses. ‘Would’ is also used to form tenses, but more importantly, it is used in most conditional sentences in the English language.
First, it can mean something in the past that was habitual or regularly happened.
“We would get ice cream once a week, but that was before the parlor closed.”
It can also be used to express something that happened in the future relative to another point in the past. If, for example, someone cut their hair after having a picnic, then the haircut would be in the future relative to the picnic. This is typically shown by using the past perfect tense – the word ‘had’ before a past tense verb – on the action furthest in the past and then using ‘would’ to describe the other action.
“She had admired his long hair, not knowing that he would get a haircut later that day.”
The other main use is when something is likely to happen. This roughly means that something happened which was likely to happen, judging by the characteristics of the thing or person involved.
“He claimed he was innocent, but he would say that, wouldn’t he?”
Secondly, it can be used to express that something is conditional. That is, something can only happen if another thing happens. In this sense, it’s normally used with the word ‘if’ or ‘provided’.
“I would like to go with you if you don’t play the radio in the car.”
Similarly, it can be used to suggest that something is uncertain. If, for instance, a person is asking for an opinion on a potential vacation idea, then a response with ‘would’ reflects that the vacation might not happen.
“It would be great to find the missing Doctor Who episodes, but it’s unlikely.”
Finally, it can be used to ask someone to do something.
“Would you please pass the salt?”
This is generally used for a polite request. The implication here is that the person who is asking is providing a choice of whether or not to do it; in addition to the request, they’re asking if the person is willing to do it. It can still be used for impolite requests, but that does not happen as often. The other main use in questions is to ask for an opinion.
“Would you like to go to the Bahamas next month?”
In the past, ‘would’ had some different meanings. While these are not found in modern English, there are a number of older works using ‘would’ in this way and some of them are still commonly read, such as the works of Shakespeare. It has always been the past tense form of ‘will’, but back then, ‘will’ also meant to wish for something.
“I would that he fell into a pit and broke his neck.”
This is still sometimes used in phrases, such as ‘would rather’ or ‘would to God’, but these are not commonly used.
Another possible meaning was ‘want to’. The ‘to’ was implied to be in the verb, so it could be used directly with a ‘be’.
“He would be thought a great mystic.”
There are a few other uses of the word ‘will’ that have a different past tense form. It can mean trying to make something happen through the power of someone’s mind and leaving instructions after death. For those meanings, the word ‘willed’ is used as the past tense. ‘Would’ is only used for past habitual actions, future past events, things that were likely to happen, and conditional or uncertain things.