Final answer:
A beta particle, symbolized by the Greek letter β, is equivalent to an electron and is emitted from the nucleus during radioactive decay.
Step-by-step explanation:
The form of radiation that is equivalent to an electron is a beta particle, which is symbolized by the Greek letter β (beta). A beta particle is a high-speed electron that is ejected from the nucleus of an atom during radioactive decay. In contrast, an alpha particle consists of two protons and two neutrons, equivalent to a helium nucleus, and gamma radiation is a very high energy form of electromagnetic radiation, much higher than X-rays.