massless

This term is primarily a technical descriptor used within the fields of theoretical physics and quantum mechanics. It describes particles, such as photons or gluons, that possess zero invariant mass, allowing them to travel at the speed of light. In these scientific contexts, the word is precise and neutral, devoid of the metaphorical connotations of lightness or agility found in everyday language.

Outside of a scientific framework, the word is rarely used. When applied to non-physical objects or abstract concepts, it may suggest a lack of substance or importance, though such usage is non-standard and typically replaced by terms like "weightless" or "insubstantial."