(chemistry) any of the electrons in the outermost shell of an atom; capable of forming bonds with other atoms

A leptonic elementary particle, having near-zero mass and no charge

(physics) Any of several electronic devices that control electron current through vacuum, gas or vapor between electrodes within a sealed container, usually of glass or metal and often designed to be easily installed in and removed from the equipment in which it is used.

(chemistry, physics) An electron, in an atomic orbital, for which there is no other electron in the same orbital but with opposite spin; a characteristic of free radicals and other reactive species

Any of several forms of microscope that use a beam of electrons, rather than one of light, and thus has a much greater resolving power.

(physics) A measure of the probability of finding an electron at a specific location within an orbital / (physics) A measure of the number of electrons per unit volume of space.

(physics, chemistry) The arrangement of electrons in an atom, molecule, or other physical structure like a crystal.

(physics) Any device that produces a stream of electrons, especially a narrow stream that is focused onto a phosphor screen.

(chemistry, physics) Two electrons having opposite spin but all other quantum numbers the same; i.e two electrons in the same atomic orbital or molecular orbital, especially such electrons that function in concert to form a covalent bond

microscopy carried out using an electron microscope