Rutherford coined the terms alpha ray and beta ray in 1899.
Ernest Rutherford developed the names while investigating two kinds of radiation released by radioactive materials. They differed in how strongly they penetrated matter: alpha radiation was less penetrating, while beta radiation traveled farther through materials. The Greek-letter labels provided a practical way to distinguish the emissions during the rapidly developing study of radioactivity.
The work grew from Rutherford’s investigations of uranium radiation and from the influence of Henri Becquerel’s 1896 discovery of spontaneous radioactivity. Rutherford’s experiments showed that radioactive emissions were not identical to Röntgen’s newly discovered X-rays. His classification became a foundation for later nuclear physics.
Rutherford later added a third term, gamma ray, in 1903 after recognizing the highly penetrating radiation studied by Paul Villard. The names alpha, beta, and gamma remain standard descriptions of three major types of nuclear radiation, although modern physics explains them more precisely as helium nuclei, electrons or positrons, and high-energy electromagnetic radiation.