would

would /ˈwʊd/ /wəd/ /əd/ verb
would
/ˈwʊd/ /wəd/ /əd/
verb
Britannica Dictionary definition of WOULD
[modal verb]
1 
— used to indicate what someone said or thought about what was going to happen or be done
2 
— used to talk about a possible situation that has not happened or that you are imagining
3 
— used with have to talk about something that did not happen or was not done
4 
— used to say what you think someone should do or to ask for someone's opinion about what to do
5 
— used to say that you want to do or have something
6 
— used to ask a polite question or to make a polite request, offer, invitation, etc.
7 
a  — used to say that you are willing to do something
b  — used in negative statements to say that someone was not willing to do something
8 
— used to express a wish
9 
— used to express your opinion
10 
— used to talk about something that always or often happened in the past
11 
— used with so (that) to explain why something was done
12 
— used to say what you think is probably true
13 
— used to say that something is possible or likely
14 
— used to express your displeasure with behavior that you think is typical of someone
15 
old-fashioned + literary — used to say that you wish something was true, had happened, etc. — usually + that

how would I/we know

— used to say that you do not know the answer to a question and are surprised that you were asked it