Dear Sofia,
"Because obviously you are all common with what you are meaning by using the term 'pus', we but once thought also to understand it, but now came into an embarrassing situation." Do we nowadays have an answer to what we mean with the word 'pus'? Not at all. And that's why the question about the meaning of pus has to be asked again. Are we today even in the situation of not understanding the expression 'pus'? Not at all. And so first of all, an understanding for the meaning of this question has to be woken.

Yours,
John