そんなはずがない

The phrase is a combination of several elements: * **そんな (sonna):** This is a demonstrative adjective meaning 'such,' 'that sort of,' or 'like that.' It refers to something previously mentioned or understood in the context. It is a contraction of 'そう (sou)' meaning 'so' or 'that way' and 'な (na)' an attributive particle. * **はず (hazu):** This noun expresses expectation, likelihood, or a natural consequence. It indicates that something 'should' or 'is expected to' be the case, or conversely, in negative constructions, that it 'should not' or 'is not expected to' be the case. Its origin is debated, but one theory suggests it comes from '筈 (hazu),' a bowstring notch, symbolizing a fixed point or certainty. * **が (ga):** This is a grammatical particle that functions as a subject marker, but in this construction, it often acts to emphasize the preceding element or to connect clauses, adding a slight pause or contrastive nuance. * **ない (nai):** This is the negative form of the verb 'ある (aru)' (to be, to exist for inanimate objects) or an adjective ending. Here, it negates the 'hazu,' meaning 'there is no expectation' or 'it is not the case.' Combined, 'そんなはずがない' literally translates to 'There is no such expectation/likelihood' or 'That kind of thing is not supposed to be.' Over time, it has evolved into a strong idiomatic expression of disbelief or impossibility.