·        The electron mass is a fundamental observable requiring no further fundamental explanation.

·        Invariant mass is the bare mass of a particle along with the mass contributions due to virtual particles temporarily created by the force fields around the particle. In some theories bare mass may be plus or minus infinity. In electroweak theory involving the higgs boson the bare mass of all particles is taken to be zero. The measured mass is given by M= bare mass +dm where dm = increase of mass due to interaction of particle with the medium or field.

·        free electrons are accompanied by their em  field self field since they are dressed. dressed particles are on shell.

·        bare particle..an excitation of an elementary quantum field. real, particles are dressed and include additional particles surrounding the bare one ie excitations of other fields. dressed electrons include the presence of electron positron fields and photons.

·        bare charge eg proton .. charge it has due to itself only and not modified by surroundings particles.

·        electron interactions ..........elastic inelastic etc

·