Plural of flaccidity; multiple instances or types of being soft, weak, or without firmness.
From flaccid (from Latin flaccidus meaning 'slack' or 'weak') plus -ity (state or quality) plus -ies (plural), creating a plural noun.
Flaccidities is almost never used because people rarely need to discuss multiple types of softness, but it proves that English grammar allows us to pluralize abstract qualities even when practicality doesn't call for it.
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