Plural form meaning multiple instances or times when something is accessible, ready for use, or when someone is free.
From 'availability' (the quality of being available) plus the plural suffix '-ies.' The root traces to Old French and Latin, with the modern noun form solidifying in English by the 17th century.
Scheduling software that aggregates availabilities from multiple people is essentially solving a complex mathematical problem called constraint satisfaction—something computers are exponentially better at than humans trying to find a meeting time.
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