Comparative form of bitter; more bitter or possessing a greater degree of bitter taste or bitter emotion than something else.
From 'bitter' plus the comparative suffix '-er.' While 'more bitter' is now standard, 'bitterer' remains valid in English, particularly in older texts and some dialects.
English has two ways to compare adjectives—'bitterer' (the old-fashioned Germanic way) and 'more bitter' (the newer Latinate way)—and both are correct, showing how English constantly evolves by mixing different linguistic traditions.
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