zeroth

Zeroth is an ordinal adjective derived from zero, used to designate the position of something at index zero or as a preliminary principle preceding the first. In mathematics, computer science, and physical sciences, zeroth denotes a starting point or an element that comes before the first.

In programming, zero-based indexing is common: the first element of an array or list is at index 0, which influences how arrays are accessed, how loops are written, and how algorithms are designed. Many widely used languages adopt this convention, including C, Python, JavaScript, and Java. The concept of the zeroth element is therefore the predecessor to the first element in a sequence.

In physics, the Zeroth Law of Thermodynamics is a foundational principle stating that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This equivalence justifies the measurement of temperature as a property that can be consistently compared across systems.

In science fiction and robotics, the Zeroth Law of Robotics appears in Asimov's works. It states that a robot may not harm humanity, or, by inaction, allow humanity to come to harm, effectively superseding the original Three Laws when considered at a larger scale.

Other uses include historical, mathematical, or computational contexts where a sequence or framework begins with zero. The term emphasizes a baseline reference point that precedes the conventional starting point in a given system or theory.