The word "copiosities" is not a commonly used term in English, which makes its spelling peculiar. The first syllable is pronounced as "koh-pee", with a long "o" sound and a soft "c" sound. The second syllable is pronounced as "oh-SIT-eez", with stress on the second syllable and a typical "s" sound in the end. The word means abundance or a large quantity of something. While it may not be encountered often, knowing its spelling and pronunciation can come in handy in certain contexts.