訳(わけ)がないThere is no way, There is no reason, It is impossible, Cannot be

The grammar point ことはない often indicates that there's no necessity or need for something to happen, or it describes a situation that never occurs. On the other hand, わけがない implies a stronger and more definitive impossibility, meaning "there's no way" or "there can be no reason" for something to happen or be true. In other words, ことはない refers to optional or non-occurrence, and わけがない denies the possibility or likelihood of an event or statement.

The phrase はずがない is often used when the speaker has some sort of expectation or logical basis for believing that something won't happen or isn't the case. Meanwhile, わけがない is typically used when the speaker refutes a claim or thought because they believe it's unreasonable or illogical. While both phrases express impossibility, はずがない usually implies an unmet expectation, while わけがない indicates the speaker's affirmation of impossibility beyond doubt.

The phrase わけではない is used when you want to deny a certain interpretation or assumption of a situation or statement, similar to saying "it's not necessarily the case" in English, leaving open the possibility of other alternatives. On the other hand, わけがない is a more definitive and stronger denial implying "there's no way" or "it's impossible", indicating that the situation or statement could not be true or occur under any circumstances.

The grammar point わけがない emphasizes that something is impossible due to a lack of logical reasoning or justification, while ようがない・ようもない stresses that there's no method or way to accomplish something. So, if you're expressing that something is impossible due to structural conditions or physical impossibilities, you would use ようがない・ようもない, but if a conclusion or assumption is logically impossible or absurd, you would use わけがない.

The grammar point そうもない suggests that something is "very unlikely" or "does not seem likely" based on a certain judgement or observation. It leaves room for possibility, however slight. On the other hand, わけがない is used to state something is impossible or there is no way for something to happen, displaying a strong sense of certainty. It tends to be more absolute and definitive than そうもない, eliminating room for possibilities.