polarity-flipping adverbs

Japanese has a class of adverbs (あまり, なかなか, ほとんど, めったに, 全然, 決して) whose meaning depends on the polarity of the predicate. Many flip from 'much/often' in affirmative to 'hardly/never' in negative — あまり食べる 'eat a lot' (rare usage) vs あまり食べない 'don't eat much.' Recognizing this pattern is essential for reading negation correctly.