In 1983, the metre was redefined in the International System of Units (SI) as the distance travelled by light in vacuum in 1/ 7008299792458000000â 299792458 of a second. As a result, the numerical value of c in metres per second is now fixed exactly by the definition of the metre.
Blattodea is an Order of insects containing the cockroaches. Cockroaches first evolved around 350-300 million years ago and are probably one of the most despised of all insects. For some people the mere mention of cockroaches will send them running for cover.
Medical Definition of mandible. 1  1a: jaw 1; especially : jaw 1bb: the lower jaw with its investing soft parts. 2  2: any of various invertebrate mouthparts serving to hold or bite food materials; especially : either member of the anterior pair of mouth appendages of an arthropod often forming strong biting jaws.