Thermionic
Part of speech: adjective
Definition: concerning the emission of electrons from a heated electrode
Particle
Part of speech: noun
Definition: A body with very small size; a fragment.An elementary particle or subatomic particle.A word that has a particular grammatical function but does not obviously belong to any particular part of speech, such as the word to in English infinitives or O as the vocative particle.
Example sentence: We have now seen that there is no particle of evidence for the Egyptian origin of Tarot cards.