Collocations are recurrent combinations of words where one lexical item occurs near another lexical item with a frequency far greater than chance. Collocations can be used to study meaning. I argue that the collocational phrase ‘really know’, in conjunction with some reasonable interpretive conclusions, provides us with evidence that the verb ‘know’ has an infallibilist sense. I make my case, first, by arguing that ‘really’ when part of the phrase ‘really know’ is best understood as synonymous with ‘truly’. I then (...) argue that there are two plausible interpretations of the function that ‘really’ plays in the phrase ‘really know’. On the first interpretation, ‘really’ helps distinguish claims about genuine infallibilist knowing from loose talk about ‘knowing’. On the second interpretation, ‘really’ is often used to disambiguate an infallibilist sense of ‘know’ from a fallibilist sense of ‘know’. On either interpretation, there is an infallibilist sense of ‘know’. (shrink)