Thomson's hypothesis is a concept in physics that proposes that atoms are made up of smaller particles called electrons. It is a fundamental principle that has helped shape our understanding of atomic structure since its inception. While there may not be any direct synonyms for this phrase, there are related terms that describe the same or similar concepts. For instance, atomic theory, quantum mechanics, and subatomic particles all relate to the study of atoms and their fundamental components. This field of science has led to numerous technological advancements and is critical to many scientific disciplines, from chemistry to materials science and beyond.