Should

Should is to shall as would is to will, except that should is common even in dialects where shall is not.

In some dialects, it is common to form the subjunctive mood by using should: "It is important that the law should be passed" (where other dialects would say, "It is important that the law be passed") or "If it should happen, we're prepared for it" (or "Should it happen, we're prepared for it"; where early Modern English would say something like, "If it happen, we're prepared for it," and many dialects of today would say, "If it happens, we're prepared for it").

Should commonly describes an ideal behavior or occurrence; for example, "You should never lie" means roughly, "If you always behaved perfectly, you would never lie"; and "If this works, you shouldn't feel a thing" means roughly, "I hope this will work. If it does, you won't feel a thing." In dialects that use shall commonly, however, this restriction does not apply; for example, a speaker of such a dialect might say, "If I failed that test, I think I should cry," meaning the same thing as, "If I failed that test, I think I would cry."