A more thorough explanation:

Definition: Intercalare (in-tər-kə-lair-ee) is a Latin term used in civil law to mean introducing or inserting something among others. This can include adding a day or month to the calendar.

Example: In ancient Rome, the calendar was based on the cycles of the moon. However, this system did not align perfectly with the solar year, causing seasonal drift. To correct this, the Romans would intercalate an extra month, called Mercedonius, every two to three years.

Explanation: The example illustrates how intercalare was used to insert an extra month into the calendar to keep it in line with the solar year. This ensured that important events, such as religious festivals and agricultural activities, occurred at the appropriate time of year.