A Dirac fermion is a type of particle that follows the principles of quantum mechanics and special relativity, described by the equations formulated by physicist Paul Dirac. These particles have half-integer spin, which means they are classified as fermions, and they obey the Pauli exclusion principle, allowing them to occupy the same quantum state only under certain conditions. Dirac fermions are significant in the study of condensed matter physics, particularly in materials like graphene and topological insulators. In these materials, they exhibit unique properties, such as high electrical conductivity and the ability to behave as massless particles, leading to potential applications in electronics and quantum computing.