筈(はず)がないHardly possible, Cannot be, Highly unlikely, Improbable

These forms are opposites. はずだ expresses positive expectation, as in 来るはずだ ('He should come.'), while はずがない strongly denies a possibility based on logic or knowledge, as in 来るはずがない ('There's no way he'll come.'). Both are grounded in reasoning, but the conclusions differ.

はずがない denies something based on logic or evidence, while わけだ draws a conclusion or explains a reason. For example, 来るはずがない ('There's no way he'll come.') vs. 来るわけだ ('So that's why he's coming.'). One rejects a possibility, while the other clarifies it.

はずがない strongly denies something, as in そんなことがあるはずがない ('That can't possibly be true.'). In contrast, ないことはない suggests that something is technically possible, but maybe unlikely or difficult, as in 行けないことはない ('It's not that I can't go.').

ことはない has two primary uses: one is to express that there is no need to do something, e.g. 心配することはない ('There's no need to worry.'), and the other is to say that something simply doesn't happen, e.g. 彼と会うことはない ('There are no cases where I meet him.'). In contrast, はずがない expresses the speaker's strong denial or disbelief regarding some possibility, e.g. 負けるはずがない ('There's no way / It's highly unlikely we will lose.').

Both express strong denial, but ものか is more emphatic and emotional. はずがない states something is unlikely or impossible, based on logic, e.g. 来るはずがない ('There's no way he'll come.'). ものか rejects something outright, as in 君にできるものか！ ('As if you could!').

Both express strong denial, but their usage differs. まじき is a formal, literary expression usually found in fixed phrases such as あるまじき, and is used to judge that something is morally or socially unacceptable rather than logically impossible, as in 指導者としてあるまじき行為だ ('It is behavior unbecoming of a leader.'). はずがない denies possibility based on logic, evidence, or common sense, stating that something cannot be true, as in 彼がそんなことをするはずがない ('There is no way he would do such a thing.').

These both express impossibility, but in different ways. はずがない asserts a strong disbelief based on knowledge, like 雨が降るはずがない ('It can't possibly rain.'). ようがない・ようもない focuses on the lack of a method, as in 連絡のしようがない ('There's no way to contact them.').

はずがない strongly rejects something as being true. わけではない denies an assumption while leaving room for nuance. For example, 雨が降るはずがない ('There's no way it will.') vs. 雨が降るわけではない ('It's not that it will rain.'), implying e.g. that the weather might be poor in other ways, etc.

はずがない and わけがない are similar in that they both express a strong denial of a possibility, similar to the English 'There's no way that (A)', but with slightly different nuances. はずがない gives the sense that the speaker is drawing a conclusion based on their own reasoning, often with a sense of surprise or disbelief. In contrast, わけがない expresses an even stronger denial, as if the impossibility is an obvious fact.

そうもない and はずがない both express the improbability of something happening. そうもない is the less confident of the two and carries the nuance that something seems unlikely, e.g. 雨が降りそうもない ('It doesn't appear that it's going to rain.'). In contrast, はずがない is a stronger denial, with a nuance of disbelief or surprise, e.g. 負けるはずがない ('There's no way / It's highly unlikely [we] will lose.').