Sentence:  At once my ears were drowned by a flow of what I took to be Spanish , but - the driver 's white teeth flashing at me , the road wildly veering beyond his glistening hair , beyond his gesticulating bottle - it could have been the purest Oxford English I was half hearing ; I would n't have known the <WSD>difference</WSD> . 
Meaning of the word marked with <WSD> tags:  the quality of being unlike or dissimilar