# What is the mass of an electron?

${m}_{\text{rel" = m_"rest}} / \sqrt{1 - {v}^{2} / {c}^{2}}$
However, as the time-independent Schrodinger equation involves what are called stationary states, we tend to use its rest mass in calculations, defined as ${m}_{e}$:
${m}_{\text{rest" -= m_e = 9.10938291_(40)xx10^(-31) "kg}}$,