The specific location or moment where a series of actions or processes begins, often considered a reference for subsequent measurements or calculations.

A designated reference point used for measurement or calibration, serving as a basis for direction, distance, or time calculations.

The initial stage or location that marks the commencement of an event, journey, or process, contrasting with the endpoint.

A crucial point that establishes the context for further developments or actions, often used as a foundation for understanding subsequent occurrences.