"let alone" e.g. I wouldn't go near an alligator, let alone pet one. When using this phrase we want to emphasize that it would definitely be out of the question to even consider, what follows the "let alone" clause, in this case, 'pet one'. Much/even/still less: used after a negative statement to emphasize 'more' on the degree of negativity. e.g. I hardly have time to go on a weekend getaway these days, (much/even/still less) a vacation! I hope this helps!