IPA: /ˌɪn.təˈkeɪ.ʃən/
KK: /ɪnˌtɜr.kəˈleɪ.ʃən/
The act of inserting something into an existing sequence or structure, often referring to a layer or period added to a calendar or the insertion of a molecule between others.
The intercalation of an extra day in February helps to keep our calendar in sync with the Earth's orbit.
Intercalation → It is formed from "inter-" (meaning between) and "calare" (meaning to call). The word refers to the act of calling or inserting something between other things, often used in the context of adding extra days or months to a calendar.
Think of inserting something 'between' ('inter-') other items, like adding extra days to a calendar, which is what intercalation means.