Ground state refers to the lowest energy level of an atom, molecule or nucleus. While this term is widely accepted in quantum mechanics, there are other phrases used to describe it in different contexts. In nuclear physics, the term "nuclear ground state" is often used, while in chemistry, scientists refer to it as "lowest energy state". In atomic physics, "fundamental state" is another synonym, and in quantum field theory, "vacuum state" is used when referring to the lowest energy level of the universe itself. While each synonym describes the same basic concept, the nuance in phrasing can help clarify meaning within specific scientific fields.