(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

(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.

(uncountable, networking) Email (the system). / (countable, dated) An email.

(physics) A unit for measuring the energy of subatomic particles; the energy equal to that attained by an electron moving through a potential difference of one volt. Equivalent to 1.6022 x 10⁻¹⁹ joules.

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

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

A book published in electronic form.

(music) A keyboard musical instrument, resembling a spinet, or upright, piano in size and general shape, in which tone is generated by electronic circuits and radiated by loudspeaker.

(quantum mechanics) The field concerned with the interaction of radiation and matter, and on the effects of quantum mechanics on the behaviour of electrons.

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.