Fluorescence

This word is defined as "the emission of electromagnetic radiation, esp. of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued." "Fluor-" comes from the Latin word fluere, meaning "to flow," and "-escence," denoting a state or process, comes from the Latin suffix -escentia, which came to our language through French.
I think that it is interesting that this is a word very commonly used in our day and age, but one that is most likely not understood entirely by most people who use it in terms of its true meaning ... it's sort of a testament to the way in which technology is now taken for granted.