Intercalation

Part of speech: noun

Definitions

1. The act of adding an extra day or month into a calendar to realign it with the seasons ; the process of inserting atoms or molecules between layers in a layered material's structure
2. The introduction of an additional time period into a calendar system to correct seasonal drift ; the chemical or physical insertion of species between planes in a crystalline or layered solid
3. A calendrical adjustment involving the periodic addition of days or months to maintain alignment with astronomical cycles ; the incorporation of molecules or ions between layers of a compound without disrupting its overall structure

Etymology: The Roman calendar gave intercalation its first and most literal meaning. Latin "intercalare" combined "inter" ("among") with "calare," meaning "to call out" or "proclaim," so to intercalate was to announce an extra day inserted between existing ones. The reason was practical: the year of twelve lunar months falls short of the solar year, so priests had to add days or months at intervals to keep festivals and the seasons in step. The calling-out sense survives in the way a proclamation marked the added time. The word later stretched to cover any insertion between existing layers. In the sciences, it describes atoms or molecules slipped between the sheets of a layered material, such as graphite or clay, which pushes the layers apart and changes the material's properties. The calendar sense and the chemistry sense share only the idea of something placed between things already in order.

Synonyms: insertion, interposition