the principle that a ray of light passes from one point to another in such a way that the time taken is a minimum
Fermat's principle in American English
noun
Optics
the law that the path taken by a ray of light in going from one point to another point will be the path that requires the least time
Word origin
[1885–90; named after P. de fermat]This word is first recorded in the period 1885–90. Other words that entered Englishat around the same time include: booster, foregut, retread, sensitization, twofer